Fairport-A4

Hi - I'm new to Audi and this forum, so please forgive my potential ignorance. I'm trying to find the cause of a P0303 CEL code. I bought my 1999 A4 2.8 Quattro (AHA engine) from a friend this past summer. Only 80K miles and well kept - all service records, routine maintenance always performed, etc. Current milage is 83K. I was driving down the highway at about 72 MPH when the vehicle started to run very roughly, the CEL came on and also flashed on and off during acceleration. I ran OBDII scanner diagnostics and determined the CEL was for a P0303 - Cylinder 3 Misfire Detected.

Rather then read through a stack of old service receipts to see if/when the plugs & wires were replaced, I just decided to replace the plugs and wires and then have a baseline for future reference. The problem didn't go away. I swapped the cylinder 2 & 3 wires and the problem remained on cylinder 3. I tested the compression and verified that the compression was the same on all 6 cylinders. I also verified that cylinder 3 was firing via in-line spark test. I haven't checked the injector yet, but that would be the end of the line for me as far as trouble shooting goes. I don't have the expertise to do much more - as I am just an aspiring backyard/weekend mechanic. I am posting this thread with the hope of gaining some insight as to other potential causes of a cylinder misfire. Any assistance would be greatly appreciated!