I recently had PBD tune my car. I opted for the E85 tune as well, and as a bonus, was given a Flex Fuel tune, as they saw it as a 'novelty' tune. The 93 tune went very well, and since today, 04/29 has been one of the first days without rain, I got the car out. Seeing as the car sat for the Winter with a full tank of 93, I drove the tank down to about a quarter and then filled up with E85 and flashed the car with the FF tune. Not sure what it did, but I can barely drive the car now. It seemed fine for about the first 15 miles. Seemed smooth, but as soon as I hit the gas, the car bucked, and got a message on the dash that active exhaust was not available. I let off the pedal, and the car smoothed back out. I informed PDB about this, and they told me to do a KAM reset on the car, which I did. After the KAM reset, I took the car back out, and it was even worse! It dies at idle now, and along with bucking, it's now backfiring as well. I don't want to ruin the engine, but don't know what else to do. Has anyone else experienced this type of thing when going to Flex Fuel?