95 firebird 3.4L backfiring on 4000rpm no power

[dobemakedonec]

I need help.firebird 3.4L runs good until 3000 rpm after that start back firing thru the intake no power and is so hard to go 5500rpm.no check engine light I do tune-up plugs fires fuel filter install new catalytic injector flush good fuel pressure.on idle is perfect good gas milage but no power.If anybody have simular problem please help me.thanks

[wrightz28]

Originally Posted by dobemakedonec

good fuel pressure.on idle is perfect good gas milage but no power.If anybody have simular problem please help me.thanks

Are you checking the pressure at idle only? If so, you need to take it under the driving cirumstance of when the problem occurs.

[dobemakedonec]

I drive the car with fuel gauge on it fuel pressure ia ok I have 35-40 psi