2003 Suburban, 2WD

I've been fighting with reduced engine power for a while on my suburban. I've read many post about this issue but still fighting with it. I feel Im getting close to the issue but cant quite pin it down. The previous owner put on a new throttle body, I have changed the accelerator pedal assembly, battery, all coil packs, plugs, wires, TAC module, throttle position sensor connector, and just swapped the accelerator pedal assembly again. I've also checked the grounds on the rear of the engine block, and the two under the drivers door, replaced the ground connector on the ground cable to the battery. The first time I replaced the accelerator the issue went away for over 6 months, then started coming back slowly. Now, after swapping it again and the TPS connector, it only seems to go into REP if I get down hard on the accelerator. If i drive with a lite food (I do mostly) it doesn't give me any issues. At this point Im thinking its in the wiring, or connector going to the accelerator pedal assembly, but all the wires look good from what I can see. The CEL does come on, but goes out before I can get to the parts store to check the codes. I have 2 readers but for some reason they do not work on this suburban.

1) What would someone suggest as my next step on tracking this down? I'm thinking about changing the throttle position sensor because I'm not sure where the other owner got it from, but it looks brand new, and I hate to keep throwing parts at it.

2) Im looking at some of the OBD scanners on Amazon that have a larger screen that gives more info ($150 range). If I pick one up, is there something I can look at or monitor to try and see where the issue is coming from? Signal from the pedal to the TPS or something like that? All mine are the small hand held that just gives codes.

3) I've been told that from changing the TAC module and pedal that I should take it to the dealership for them to resync it in the computer, I called one dealership and they told me yes that it needs to be done. I called a 2nd one closer to work and they said no, there is no need to do it on this modal suburban. Im not sure what to believe.

Thank you for any help.

 

You can buy an OBD II unit that gives trim codes but they are 150-200 dollars or more.

I ihave an Innova 3160g. Gets the job done well.

 

I'm looking at a few different scanners in the $150 to $400 range, but not sure what I really need. Just this morning I found OBDWiz cable that goes into a laptop, I think I will give it a try, its only $30 and the software is a free download. I'm still not sure what direction I need to go from here to repair this issue. I guess once I get the cable I will see if I can compare the signal from the accelerator to the signal to the throttle position sensor and see where the issue is.