I've been having issues with my a4 for a few weeks now, I've tried several solutions and haven't been able to solve this issue.

Some of the most common solutions for fixing the p303 have been to replace the coil, spark plug and injector. I've done all three of those, the car will work fine for a few days before reverting back to old form. There is a sputter/loss of horsepower constantly while I'm driving it.

Anyone have any idea what could actually be causing this problem?

 

Check the harness for cracks or tears. This is a common problem. Start at #3 coil pack and work your way back