I was looking to buy an audi90 quattro and i was wondering hhow much stock hp they have and dose anyone have a list of mods for them thanks

I believe stock hp for the 20v is 165ish. The best way to add power is with a turbo. Supposedly, its not advised to add just the turbo because the lower end isnt built for it. So, you need to rob a complete turbo motor and harness from another car. As far as I know, the little hp add-ons are worthless. The car needs brakes, suspension, and a turbo. As always for brakes, add calipers with more pistons, drilled/slotted rotors, and steel braided lines. For suspension, you can get some sport springs and new shocks, or get a nice coil over kit. If you shop around, you should be able to find a totalled 200 turbo quattro to get the motor from. From what I can tell, its not that tough of a job to swap, just time consuming. ie: dont do it to your daily driver.

How much do you think I would be able to pull all of that off for

You might be able to find a donor car for $1000. Suspension anywhere from $300(shocks and springs) to $1200(coil over kit). Brakes im not sure....maybe $500ish. But, you would have a friggin fun car. I have a 5ktq that im thinking of parting out. Im tempted to find a 4kq for cheap and do the swap.

Do it!