From simple to not so simple, you can:
1. Take everything (not fixed to the car) out: spare tire, jack, carpets (at least the detachable ones), ashtrays, cigarrette lighter, windshield wipers. Empty the windshield water tank, or better yet, take it out (normally that's simple to do). Use the less amount of fuel possible. Clean all the dirt from under the car (use a high pressure hose) and wax it.
2. Then, try to remove things not-so-attached: radio, speakers, sun shades, rearview inner mirror (you won't need it!), glove compartment lid. Sometimes the rear seat can be easily extracted and repositioned after the race. If you remove the "fixed" carpets, go on and remove the rubber plugs in the floor (mark them!). Remove headrests (not the one of the pilot). Don't if you race with people on board (why would you?
). If you are really mad (it's probable...), use lighter clothes, cut your hair, don't eat before the race, do as Kimi does (take a dump before the race).
3. For a short run, you could try to take the air filter out and recarburate. For a permanent fix, use a bigger air filter. Check if the "Turbonator" you propose gives you the same power increase: this could be the reason. I can hardly believe that gasoline could be more "vaporized" than what already is, but apparently you can return this gadget (be careful with the sending/handling charges, some people that sells by mail live on them).
4. Change the ECU EPROM chip. I have no idea if they are available for your friend's car, but they are cheap and easy to change.
5. Reprogram the ECU. Check
here for an example about how to do it. Sometimes you can lease/borrow an EPROM reader/programmer. This takes time, some intuition and a lot of testing.
6. For a short run, take the exhaust pipe out. For a permanent fix, use bigger pipes. This should go higher in the list, but you can change the exhaust heads and/or the catalytic converter for a high-flow one.
7. Use an underdrive pullie (I'm not sure if this is the correct english name). There are crankshaft and alternator ones. They are bigger pulleys that reduce the drag of accesories. The alternator will run slower and may not charge the battery when the engine is on idle, so some people use only crankshaft ones. I've heard you can get 10 to 15 hp only on that (on large cars, like my GTO).
8. Get a tachometer. Shorten the shifting bar to make smaller movements when changing gears. Recalibrate the clutch and try to make the clutch movement as short as possible. Squeeeeeeeeze the throttle instead of pushing it... (well, I don't know how else to put it). Practice gear shifting. Practice. Practice. Take your times once and again.
I have a confession to make here: I sing while I drag-race, it gives me rythm to shift gears... You have to find a song for every car, timing is different: my old GTO "goes" with Boston's "Don't look back", my wife's Sentra has the gears "sinchronized" with Rolling Stones "Start me up". My age is notorious, isn't it?
Actually, you can use any song: find the shifting points in it. In an unknown car, sometimes I use the third movement of the 9th Beethoven's Symphony (it has one beat per second rythm! I use my microwave clock to time myself: I try to hum or sing to figure out when it's going to beep. I can do it pretty well after many years, so I have a consistent rythm). Please, don't make jokes on me because of that or I won't tell you anything again.
I think sometimes that driving "with" a car and dancing with a woman are similar. You breath 12 or 13 times per minute in these situations (I swear I do!): try to breath at the rythm of the curves (I'm talking about the curves of the track, not the curves of the women!
). It's the same when you do weight-lifting, if you get my drift. Notice that when you turn the steering wheel you exhalate automatically and when you straighten it you inspire. In a kart, this twisting of the arms will shift your weight toward the front in curves (or the rear in straights) automatically, so you exhale on the entrance and inhale on the exit.
End of confession.
9. Analyze the torque curve of your car and do some math. Some race simulators allow you to change the gears and try for the best combination. Try to do a simulation before following Manchild advice.
From here on, things get complicated. Definitely you won't do it for next weekend, but...
10. Use a high performance ignition system. You'll have to change the spark plug gap and put special cables.
11. Lower the car changing springs/shock absorbers to minimize weight shifting. If you were in a Corvette, you might want to lower only the rear end. Do some math (check the example of the Corvette acceleration and the resulting lack of grip at Brian Beckman's Physic of Racing). If you are "into it" you could borrow a Brembo card and height sensors (they are extremely affordable at this point of the list) and use your data like Ross Brawn would...
At least, check camber/caster and alignment of driving axle or rear wheels. Check your wheel bearings and its lubrication. Check if your braking pads return completely, if you dismount the wheels and the car has drum brakes.
12. Get a new carburator (if the car is not injected). Check which one is better for your engine.
13. Change the head or the cams. You might find 4 valve heads as opposed to regular 2 valve heads. Look for used racing cams, sometimes you can get almost new ones (check them for wear).
14. Use a super/turbocharger (well, you asked).
15. Put an intercooler on the air entrance (idem). For a short run you can try to use an ice box (yes, a box with dry ice on the removed air filter: the dry ice vapors shouldn't leak into the air entrance to the carburetor/injector). I've seen (my friends are crazy) the air conditioning piping put on top of the carburator...
Run the air conditioning before the race to cool the pipes and take the belt off the pulley for racing.
From this point onwards, check if suggestion number 18 is better (with an expert) or cheaper (check the price of parts and labor you can't do) than 16 and 17 together.
16. Change the piston rods for longer ones, or change the pistons for racing ones and use a higher octane gas (you'll increase the compression ratio). Check the actual compression pressure at each cylinder: if it is too low, don't: you risk blowing a cylinder seal ring.
17 Use bigger cylinders or rebore the block.
18. Buy a new engine.
19. Hire a proffesional driver (Villeneuve is out of work right now, for example... I'd recommend a latino, specially a colombian, they are tricky, but hey, you've to take what you get
)
20. Install a NOX system (this is the most expensive: you'll shorten your engine life). You'll have to change the fuel pipes (3/8" minimum) and the fuel pump for a high rate one: a NOX requires extra fuel to cope with the extra oxygen or you risk burning your engine. There are multiple plate systems (one injector of NOX per port) that give you three times the extra power, but they are expensive/complicated. You'll go from 100 hp for a single plate system to an extra 300-400 hp for a multiplate system.
Finally,
mandatory things: RACE IN A TRACK. Check your insurance. Buckle up. Use a helmet, gloves, racing suit if you have them. TELL YOUR PARENTS (start with your dads, give them rope: let them talk about his crazy driving days for a while, ask for permission the next day, get them a couple of beers before asking, do it when he is happy
).
You might use all your lucky charms, if you have some, only if you really believe in them. Self-confidence equals efficiency. Don't invite your friends: you don't want to be thinking about their opinion. Invite them when you're sure you'll win (that day, you'll lose).
I don't have any more time (my lunch time is over) but I'm sure I'm forgetting something...
