I was just reading over on Scuderiafans that Ferrari will be further testing some 2022 components in Austin. Apparently they will be testing a new, lighter Fuel Pump. According to the article (which I believe was quoting a Motorsport.com article/interview), some components are not Frozen like the PU and can be freely replaced.
It is true that the power unit is frozen in the development of the parts clearly defined by the FIA, but, just to give an example, there are accessories that are not part of the blocked components such as fuel pumps and can be freely replaced.
In Austin, solutions will be used that foreshadow the endothermic unit of 2022: lighter pumps will be used that will have to pass the reliability screen, in order to ensure from now to the end of the season of the duration tests in the car that will allow to homologate a “Superfast” power unit with fewer unknowns on duration, given that Wolf Zimmermann’s project promises to be with some innovative concepts.