Steviecef

<center><img src="http://pictureposter.audiworld.com/68526/vaclayout.jpg"></center><p>I have a 2000 1.8T with a GIAC chip. Its been running great till the other day. I got on it at highway speed, (80mph) and when the car downshifted and went for boost, it stumbled.

I thought for sure that I had an obvious boost leak so I made the DIY leak checker from the forum and tested. SSHHHHHHHHHH.

I found a broken check valve blowing loud and strong. Thinking I was victorious in my troubleshooting, replaced it, test drove and to my dismay, it died out again.

Just did the leak test again tonight, no leaks. I put a vacuum tester on the BPV and it seems fine too.

I did get multiple misfire and incorrect boost requested DTCs before replacing the check valve. The only VAG fault I get now is a secondary air injector, incorrect flow.

However. When checking with the VAG on the "readiness" button I get an O2 and CAT "failed or incomplete" Does that mean I have a failed CAT or O2 sensor or does it mean that since I don't have the full version that I can't read it?

I have changed the plugs as well. The car misfires and bucks with both sets of plugs.

What else could it be? MAF? Coil Pack? ICM? Who has been trough this same situation? Thanks much.

NJA4

I think some other people have. I had/have the same symptoms: occasional strong stumbling, very alarming, on WOT usually but not exclusively in 4th or 5th gear... esentially when lots of boost is called in. If I let off the gas, then resume, it's fine. If I stay on it, BAM, limp mode, EPC light. Restart and everythings fine, assuming I made it off the highway w/o getting flattened. I think it's the MAF.

Sorry, not much help looking back, but you're not alone.

Devious27t

of the turbo if you heard a sound in that area it could be torn.

Steviecef

Thanks for the responses, still not finding it, i guess I'll try the MAF next