Originally Posted by Cory Gillmore

I've had the exact same problem as you ever since a few days after getting a few mods installed and getting an ecutek tune at Z1. Car made amazing power on the Dyno (for the mods) and made the 5 hour drive home like an absolute peach. Threw the code about 3 days later on the first cool morning I left for work. Idled rough, power was lacking.

I did get mine to throw a P0305 one time (misfire cylinder 5).

Mine seems to have improved since I got the ecutek dongle and accompanying iPhone app. It ran an update the first time I connected them. Plus I cleared all the codes with it. I also tried getting gas at a different place (Shell, I usually use Exxon) and I put in a bottle of the Chevron fuel injector cleaner stuff on my last fill up.

Something I also noticed in my particular case was the problem seemed to kinda get better when my fuel level dropped below a half tank. Maybe in my head but it's something I think I've noticed.

I'm still trying to figure out mine as well, though I'm hopeful at the moment it's gone away or fixed. Keep in mind it could also be fueling ie: bad gas or a failing fuel pump or bad fuel injector. I've also wondered if maybe the fuel sending unit could play a part.

But please, for the sake of all that is holy, update this thread when you find the problem. There's way too many abandoned P0300 threads on this damn forum...I will certainly update mine, even though I've pretty much been talking to myself in there the last few days lol.