P0171 Fuel trim bank one condition...
Says probable causes are..
1- If bank one and two codes are set together suspect fuel pressure or MAF sensor
2- O2 defective (supposed to be new)
3- Ignition misfire-repair
4- Fuel injector problem

P0420 Catalyst efficiency low-bank 1
probable causes are..
1- Catalyst converter defective (failure possibly due to #2, #3, or #4)
2- Engine misfire or running condition
3- Large vacuum leak
4- Engine oil leakage into exhaust-valve guide seals,piston rings

P0174 Fuel trim bank 2 condition
probable causes are...
1- Bank 1 and 2 suspect furl condition or MAF sensor
2- Failed HO2S21
3- Ignition misfire condition
4- Fuel injector problem
5- Engine mechanical condition

The car runs like a new car, but when this **** kicks in it wont hardly rev past 4K and gets all jerky and ****

01 SS M6 113k miles. Any ideas guys??

 

You left out a key word in the P0171 and P0174 code descriptions.... "LEAN" condition.

Have you checked the fuel pressure? Should be about 58psi from idle through WOT/max engine load.

Have you checked the MAF sensor? Is is dirty? Is there any way air can enter the engine after the MAF sensor - e.g. vacuum leaks, torn rubber connectors, gaskets, etc?

For the P0420, swap the left and right after-cat O2 sensors side-to-side. If the code follows the sensor to bank 2 (P0430), its a sensor problem. If the code stays on bank 1, its a cat or wiring problem.