2003 h2 with p300 code

[agnt549]

I have A 2003 H2 Giveing me a P300 code It Has new plugs,wires,both nox senors and all O2 senors have been replaced and have had the coils tested they are fine. but still giveing the code So i toke it to the dealer they can't figer out way it is giving the code it only gives the code in the mid RPM range the dealer tested the computer said it was good. HELP need to pass Ca smog !!