This is on a 2000 A4 1.8T. I've had a heck of a time trying to figure out why my car was going into limp mode. I replaced my diverter valve and cleaned my MAF sensor. Both things obviously didn't fix the problem. It turned out to be a vacuum leak. I have outlined the culprit hose in the picture. You can see my temporary duct tape fix on the hose. Gotta love duct tape! Anyway the hose is on order and cost only 7 bucks. If anyone is having trouble with your car going into limp mode give that hose a good inspection. Mine split right at the elbow.