my gta has been having part throttle issues lately, getting worse and worse. it does not seem to matter wether its hot or cold. ill be taking off normally, the car will go forward, then seem to bog down for a few seconds, then take off with more then enough power at a little under 3000 rpm. i notice it most in 1st or 2nd. at wot there is no problem. it still runs 13.50's all day. the fuel filter is new and it had the same problem b4 the fpr and 1.6 rockers

 

You might have a dead spot in your TPS. Find a volt meter, turn the key to "on" position, but not running. Monitor the TPS voltage through a slow sweep to WOT. Should be a nice smooth progression.

Could also be a vacuum leak, dirty TB, faulty ignition piece, etc...

 

i did that with the tech 1, the tps % increases noe at a time if you slowly push the pedal to the floor

 

the throttle body has been cleaned, it has a new cap & rotor, pickup coil, distributer shaft, no vacuum leaks, new plugs and wires, nothing i have done to it has affected this, although it seems to do it worse when the motors cold

 

It could be the CTS throwing low load enrichment off. Is it throwing any codes?

 

Can you datalog and monitor what your ECM is seeing?

 

I'm having the exact same problem. It has made its way through all of my gears except 5th...
Usually only occurs in 1st and 2nd, and usually within the first 10 minutes of driving. After that though, it is fine 98% of the time.
The car runs extremely fast and well except for those few shifts every day.
I haven't figured it out quite yet. I'll post if I do. I'll monitor this thread to see if you don't find a solution as well.

 

i performed a freeze frame with the tech 1 when it happened, nothing unusual, however yesterday i was messing with it and i found that because i had to relocate my map sensor due to the fuel pressure gauge, when the motor rocks under acceleration it pulled the vacuum hose slightly, kinda hard to explain but it flexed the hose just right to cause a vacuum leak. i fixed this but i havent driven it very far yet, seems to be fixed though....