Earlier today I installed the K&N Cold Air Intake kit on my 99.5 A4. The car starts no problem, stays at it's initial high idle for a second (something like 1300RPM, can't remember at the moment), but immediately drops to <200RPM then stalls after a few seconds. If I take off the air filter and have someone hold their hand up to it and block ~90% of the airflow it will stay running at mostly normal RPMs. Now, if I unplug the MAF the car starts, idles and revs to redline just fine but of course throws a code after a bit for having unplugged the MAF. Also, plugging the MAF back in while it's running causes it to stall after a few seconds.
Could my MAF be bad, or is something else going on?
Found the problem, I'm just an idiot. I re-installed the MAF backwards (one of those kind of things where the whole process flows quite smoothly the wrong way). Flipped it around and all is back to normal.