99 blazer 4.3 drivability problem

when driving the blazer and using the gas pedal at normal/light acceleration the blazer does good. but when the gas pedal is floored or pushed all the way real fast the blazer feels like it is misfiring or hesitates to catch up. it will do this in drive and park. sometimes it will back fire when you quickly press the gas pedal all the way.

the ignition system is good, no check engine lights.

i think it might be the cat. but im not sure.

What is the mileage and tune up history?
AC delco plugs?
Fuel filter and fuel pressure readings?

140k
plugs, wire and cap an rotor are good. and coil

fuel filter looks ok, but not sure.

fuel pump and press reg, dont know i asume thay are good, the blazer went through a chicago winter ok. the car will run somewhat better when warms up but still has problem.

As MT asked - you need to test the fuel pressure and get readings or you are simply guessing and throwing effort away. Fuel filter at $15 is change every 25k and if not suer do it - no way to see in a metal can and it rules it out. As for the ingition, when were the things changed as a classic misfire is often caused by cheapo aftermarket parts such as plugs (use Delco single electrode resistor) and the ones that have biten me are the cap/rotor - always use Delco to be sure and I have had no problems with SMP or standard motor products but some others sure as Wells I will never use.

Then on to sensors or just saw a post on EGR at 2000 rpm range stuttering due to being clogged.