I found a CAI...

Honestly, you can do that, but there are much cheaper ways of making a better flowing intake. I took the air inlet restrictor off my stock airbox and then installed a K&N filter in it. Then I took the air silencer out and cut the guts out of it. It basically makes it a high-flow intake as there are no restrictions in it anymore. I did notice a gain in power and throttle response, especially when the engine was under load.
 
I read about the turbo swap in that tech thread and it sounds like a pain in the ass. Fabricating this, rewiring that, no thanks. Id rather modify an NA engine to death than do that.
 
50resto and mustangs unlimited both have something on their sites...

http://www.mustangsunlimited.com/itemdy01.asp?T1=1001P+01&Category=&catkey=lmustang

Wonder if they're the same as above, or what??

They're similar. The one from Option Racing is for '87-'90 and looks as if it sits in the engine bay while the one from Mustang Unlimited claims to be for '89-'93 and and goes into the fenderwell.
EDIT: The one from MU may be possible to use on a Mass Air car as there is a disconnect between pipes (that may, however, throw off the pipe's route to the hole in the fenderwell; also, you may need to tap your own holes to place those formerly in the airbox.