i assume, your biggest challenge will be to isolate the air filter it self, from the engine compartment.
the aftermarket products are offering some kind of metal buffer that acts as the air box.
common sense tells me, that the air inside that box, will be hotter then the OEM plastic box.
best solution IMHO, will be to fabricate some kind of a fiber glass box with multiply layers and isolation material.
not an easy job, especially when a lot of people (just like JFP) say it will result without significant results (if at all) in performance.
on another hand we have this thread:
Finally: Dyno charts of de-snorked 986S!!!
also check out this tread, and have a look at post # 127, might give you some ideas.