Recently I have developed a problem where my engine stumbles. The problem started after getting gas at a station I always go to. It feels like I am running one one cylinder. The issue seems to happen when the engine is warm. This seems to be happening when I roll on the throttle, haven't noticed it when just cruising. I stopped by my Indy and he recomended putting in Heet in case it was water in the gas. I have done this and it still is happening. 1. I took the crankshaft sensor out and cleaned it even though it didn't look dirty. 2. I put a spade across the terminals and didn't have any codes flash on the Speedo. 3. I had a TSSM code 21 (left turn signal). Don't think this would cause it. I am looking for anyone's ideas for things to look at. This is a 2002 Ultra with a 95" Stage 2 with a SERT.