I recently bought a 1991 chevy silverado 1500 stepside that needed a fuel pump, long story short I ended up replacing the fuel pump,Fuel filter Fuel lines and egr valve. When it's idling It occasionally has an issue revving up past 3500 rpms, but when your driving it down the road, you can't take it past 1/2 throttle, otherwise it starts to die/bog down, any one else have this issue, and how did you fix it. All help is greatly appreciated. Also the truck is a 5.7 4x4

 

high exhaust backpressure from clogged cats can do this. remove both up stream 02 sensors from the exhaust to bypass the restriction. if it clears up on the test drive, you have confirmed the problem.

 

Could that be the issue, cause it looks like they have been replaced not too long ago, plus if the cats were clogged up, wouldn't the truck have the same issues revving in park and neutral, as it does in drive