Engine light flashing p0300 misfiring
iv got a 2003 nissan 350z 98,000km with cold air intake, cat back exhaust, headers, and high flow cats. driving home the other day the engine started misfiring, found code p0300, and there is a code for 02 sensor heater that is older and has not been affecting anything. So far i have changed out the spark plugs. (The back 2 were soaked with oil.) I ran the car while disconnecting 1 coil pack at a time with no noticable difference. I checked the temperatures at each header tube and they are all the same. Have a new PCV. Checked the MAF which was clean and harness is good. could not find any vacuum leaks. removed intake manifold, there were no blown intake gaskets. there is oil going in the manifold going into the rear 2 cylinders. checked the resistance at each injector and they are all the same. im at 3/4 of a tank of gas, so i wouldnt think that i got bad gas. fuel mileage appears to be ok, and its not going through any oil.
does anyone know what the resistance should be for the coil packs and if thats worth checking. i think next ill do a compression test.
The engine starts misfiring about 10 seconds after initial startup and does not stop. it constantly misfires and the only way that i can even make it driveable is if i feather the gas pedal and very slowly get up to speed or else it starts coughing.
I think im running out of things to try. Any Ideas???