Sigh.... no one reads things anymore... wrong section, this section's for questions, concerns and comments and such about the site itself. I'll move it.
Is this a '93.5 MKIV or a '93 MKIII? So I can move this to the right forum... I'll move it to Gener Discussions for now.
N/A's are simply going to be louder than a turbo car, so if you're comparing the two then forget it. Also, most of the aftermarket exhausts for Supra are designed for turbo applications... larger pipe diameter, smaller resonator (if any) and so on. For a N/A I'd stick with the stock piping diameter, or up to a cm larger, add a GOOD resonator (not baffled; a helmholts resonator is free flowing but makes a very big difference), high flow cat, and a good dual tip muffler (the split for the dual tips reduces noise even more).
A CAI simply refers to an intake which pulls air from outside of the engine bay.... most modern stock intakes are CAI from the factory. People like to swap in conical air filters as the resistance to flow is generally less than OEM style filters, but they then leave it exposed and sucking in hot air from the engine bay which will cost them more power than they had lost with the stock filter... besides, just like aftermarket filters there are good and bad ones. Cheap ones are generally paper and don't flow well, some performance ones sacrifice filtering ability for ease of flow (very bad! worse than losing power due to a restrictive paper filter IMO) and some filter very well AND flow well. Filters from Apex'i and AEM's DryFlow are my preferred filters.
Post some pics of your air box and filter... there are a few possibilities as to why you may have lost power after working on the intake... including a restrictive filter, narrow inlet piping, turbulence (did you remove the helmholtz resonator by chance?), a leak in the intake after the air flow meter, damage to the air flow meter. Give some details as to what you've done and how everything's constructed.