I have a 2004 GMC Savana 3500 with the 6.0. I have been having a random misfire problem with only the p0300 code. At first I didn't notice any rough running, but now it is noticeable at idle. The light only flashes at cruising speed.
I logged misfire and cyl 5 and 8 are bad. I have run the cylinder balance test and the results were 99-100 on all cylinders. I replaced the plugs and wires today and nothing changed. I think it might have a small exhaust leak on the right side that I'm going to look into...don't know if that would cause this?
Any ideas or help would be greatly appreciated.