2001 GMC Yukon...8.1Litre (320hp, 455 fp of torque), custom built at GM with1 ton axle, beefed up radiator/cooling system & transmission.
198,000 miles on vehicle....replaced engine 3 1/2 years ago (24,000 miles on new motor)
Last October, reverse went out ... rebuit the tranny. Shortly thereafter, began loosing power and the debate began:
​​​​* Code P0742 (Torque Converter Circuit Switch Stuck On)...thinking issue with tranny.
* WITH FOOT ON THE BRAKE, PUT IN ANY GEAR, THROTTLE UP - WILL NOT POWER UP PAST ABOUT 1100 RPM
* Transmission guy says "It'* the motor" / Mechanic says "It'* the transmission"
Took vehicle to AAMCO for diagnostic testing (Snap On - Live data) ... tranny & motor....
AAMCO eliminated tranny as problem...recommended & completed tune up (plugs, wires, throttle body cleaning, injector cleaning & eliminated coil as problem)
STILL could not get past 1100, or so, RPM....So, they recommended checking exhaust system for vacuum pressure, etc.
Found issues...replaced all 4 Cat Converters & the muffler....seem to have the power back, BUT;
STILL CANNOT GET PAST ABOUT 1100 RPM WITH FOOT ON BRAKE AND THROTTLING UP IN ANY GEAR!!!!!!
Some say that this is a problem & some say that GM has put restrictor/governor into the system.

Here'* my question: Who is right? / Should I be cocerned?

How does it accelerate with your foot off the brake?

It accelerates just fine. In fact just the other day I pulled my 6900 pound boat 16 miles, into Stockton and the Marine shop, with no issues. Again, it seems as if I have the power back, but just this little issue about having my foot on the brake putting it in gear and throttling up... And if not going past about 1100 RPM

Well, don't do that!

I agree. Don't do that. I'm pretty certain that the software is programmed to prevent people from sitting there powerbraking. **** BREAKS when you do that.