98 Jetta CEL

I have a 1998 Jetta GL. It will not rev over 2500 RPM's and has a bad missfire at full throttle it blows air back out of the intake which makes the valves tick like crazy. I have replaced the rotor button, plugs, wires, dis. cap, FPR, MAS, TPS and fuel filter. I am now out of ideas and this it begaining to cost alot. Can someone please help.

Thanks
Shane

actually my jetta vr6 has the same problem except i can rev just fine. just when i floor it itll misfire sometimes and ive changed my plugs, but im gonna get wires soon. i need to go to autozone and get them to diagnose it for me. i think mine also was runnin lean. my exhaust is rusted out so i'm tryin to either build one or just take it somewhere and have custom piping run..