Hi everyone,
I have a 94 3.4L with the same problem. Acceleration is real weak, especially after 50 mph, engine seems like it's missing and everything.
Already replaced EGR solenoid, intake hoses, and spark plugs, but still no solution. What worked for any of you guys? thanks a lot for the advice, I'm a student and this has already cost me a whole lot of cash.

 

check for trouble codes.

 

Changing the plug wires fixed my 3.4L. I found that #1 was the problem. It goes around a vertical exhaust sensor pipe and had gotten too hot. It was actually broken but but the plastic wire cover was a little melted and holding it together! I didn't even find it until after getting the wire off and peeling the plastic off! I was surprised it wasn't acting worse at an idle. I had all the symptoms desribed in this thread and new wires fixed it. Watch how you route #1 wire.

 

Hard to believe but my 93 (OBD-I type computer) never got a trouble code either, even though it had to be dropping out #1 cylinder.

 

Unbelievable!!! After hundreds of dollars and weeks of horrible acceleration and performance, I finally figured out what was causing my 94 Chevy Camaro 3.4L to stumble and hesitate on acceleration and idle. I pulled out my spark plugs (which I had recently replaced) and looked at their tips one by one. I noticed that both the 3rd and 6th cylinder were completely burnt. Well if I'll be darned, the 2 cylinders that were misfiring were both connected to the same Ignition Coil! I went into autozone and bought a new ignition coil to replace the middle one for only $25 and that was EXACTLY THE PROBLEM. NOT the EGR solenoid, NOT the cat converter, NOT the intake hose, NOT the spark plugs or wires. Do yourselves a favor and check if your ignition coils are bad first before you spend any other money.

thanks for the help pweagraff!