Ive got a 1993 Audi 90s 2.8 12v...i was looking at some sites for performance upgrades...but most of the ones that have any are for the 30v 2.8 A4...i was wondering, if i could get ahold of one if the 30v would fit in the 90 with out any serious modification??? or if not if anyone new any good sites to find performance parts for the 12v...

 

I think you can do that, but then you will have to change the ECU also. If you find A4 in junk yard then its possibly good idea.
But I would search for 2.7T V6 already with upgrades without a lot of head ache.