2003 Trailblazer EXT-power, acceleration, rpm isssue

symptoms- won't rev over 3000-3500 rpm's, upon acceleration (especially uphill) seems to struggle and won't accelerate much at all, seems as if tran changes fine. BTW, throwing no codes at present.
What I have already tried...new air filter, new fuel filter, had cat. check (was told stopped up but when removed found it was not and truck did the same even with cat. off), o2 sensor (upstream) replaced, battery disconnected to reset computer.
After reset of computer, runs a little better but still not good. Seems to start if you accelerate to quickly or when truck reaches around 40-45 mph.
Any help is greatly appreciated!

Welcome to AF, first have a full scan done for pending codes in particular. Also might check fuel pressure.

battery disconnected to reset computer.

I didn't think disconnecting the battery would re-set the computer. I'm thinking it has to be done via scan tool.

You'll need a scan tool to check codes.

Does the exhaust cam advancer work properly?

Disconnreecting the battery goes back to default settings such as adaptive trans shifts and quick idle relearn, also the emissions monitors will require a drive cycle to come online, really no big deal.

scan done and no codes come up at this time. Fuel pressure is in the normal range, exhaust is not clogged past cat. How do you check the exhaust cam advancer?
how far or what driving conditions will run through a drive cycle?

From a cold satrt up a drive cycle takes from 10-20 miles of mixed hway and stop and go. If the cam actuating system was faulty it would set a code. Once the battery was disconnected the pcm has to se the condition to set a pending or live code.

thanks for all the suggestions...after trying them all and cleaning the throttle body yest...ran a little better but not much...dropped it to a trusted mechanic yest afternoon, still no scan codes showing up....will post what I find out so maybe it can help someone else down the road!

as of today my Trailblazer still has the mechanic stumped but now he is curious also and is determined to find out what is causing the problem...any other sugges:runaround::runaround::runaround:tions?

wanted to come back and let everyone know what I have found out so far, the mechanic called this evening and said he decided to take the exhaust apart and recheck even though I had been told it was no the cat stopped up. He said he took the cat back off and drove the truck, said although loud as heck (of course) ran great. So he will be replacing the cat tomorrow...wish me luck!

That is why the right way to check a cat is with a vacuum gage or a back pressure gage in the o2 port. sounds like a fix is on the way.

ok...new problem...please help someone! It turns out it is the cat but now having a unbelievable time finding the right part...what the online search at each parts site says will fit...WILL NOT FIT! the inlet/outlet measures 2 3/4" and the body length of cat is 10" and it is a spun unit...can anyone direct me to somewhere to get this part...bout to drive me crazy here!!!!!

ok...new problem...please help someone! It turns out it is the cat but now having a unbelievable time finding the right part...what the online search at each parts site says will fit...WILL NOT FIT! the inlet/outlet measures 2 3/4" and the body length of cat is 10" and it is a spun unit...can anyone direct me to somewhere to get this part...bout to drive me crazy here!!!!!
All I can say is when the cat plugged on my '03 in Kimball, South Dakota, they had a "universal" replacement shipped in the next morning, it was welded in place and we left for home later that day.

Can't be too tough to find one that'll work.