So i recently bought a 2001 1.8T A4 quattro (96,000 miles and now it has 99,000 miles). It came with the CEL light on and the modifications done to the car were a EVOMS air intake, Audi TT diverter valve, Magnaflow exhaust with a 3" down pipe and a APR tuning chip.

I took it to this shop that did a free diagnostic on it and said i had to fix a vacuum line, valve cover gasket and tensioner seal, and the O2 sensor (post cat).

I just got it back from the shop and I've replaced 3 vacuum lines, fixed the gasket and tensioner seal, replaced the O2 sensor (post cat) and changed the oil and replaced the jet suction air pump. After the 3rd time starting up my car, the CEL light came back on.

The place I took it to was a VW and AUDI specialized shop called 3zero3 motorsports. What should I do next.... is the place im going to just repairing random things...

 

is it going in to limp mode. i should have my vagcom soon and we can check it out again if you can get to one of the g2g or something.

 

i dont know what half of the stuff you just said... im very car dumb

 

lol pm me and we can try to figure something out if you still need help