Good afternoon everyone,
I have 05 base crossfire, with just over 400,000 miles. It's in pretty good condition. I have performed all the needed work myself, so I pretty much know what has been done. I'm having an issue with misfires at high speeds and high speeds only. The car drives fine under 85 miles per hour. I mean absolutely fine. The DTC or the same every time, P0302, P0305, P0306, P0300. I have changed plugs, wires, coil packs, CPS, Cam Position sensor, new battery, harmonic balancer and seal, & serpentine belt. MAF was changed less than four months ago. EGR valve changed about a year ago. All parts the recommended parts from the members of this forum (Bosch, Needswing parts) except the MAF. I have performed a vacuum test fine. Held steady between 17 and 21. Compression test fine. Every Cylinder at about 178. Fuel pump and fuel filter was changed less than a year ago. Test the fuel pressure and it was fine. Replaced intake manifold gasket ensured it was properly aligned.


That being said what could I be missing besides the Cats, bad MAF, or is it a bad ECU? Any suggestions will be greatly appreciated, except get rid of the car.