'99 A8 Quattro Performance
 

hi everyone im new to audi and im trying to see what are some cheap things i could do to add a little horsepower torque and possible improve my gas milage. i would take suggestions on any of those three.

on 4.2 engine?

hmm, there is electronics from S8 for better response and few HP, but as I know..u cant have so many Ponny under the hood and better gas mileage.
Also, modified injectors,
you can try find on ebay 3.3 TDI or 4.0 TDI for A8, 2.5TDI is too lasy. but in all thats a lot of work.

for starters change spark plugs, filters and oil, that can save few miles.

oh, yes, I saw here that you can change codes on tranny for quicker response...that could give you thrills

We don't get any diesels here in the states :( Not until recently at least! :)
As for performance you can buy a unitronics chip from 034 motorsport, a tip chip to make the shifts faster and more crisp, then add a full exhaust. That should get you around a 15-20 horse gain and about a 2% gain in gas mileage. Other than that a $20,000 supercharger from MTM is your only other option, PES might be making a supercharger for around $5,000, or they already do.

but you can buy over ebay and shiped in ,hehe

i dont think his problem with gas mileage will drop with chip tuning or supercharging it.. :-)
you cant have both..