I have a Suburban with 2 issues that im hoping are related. The first issue, which is most concerning to me is at random times the vehicle will go into "Reduced Engine Power." The vehicle will not go over 30 mph. I understand this is a common problem on GM trucks and the code can be triggered for many reasons including bad grounds or throttle body problems. I have to pull over, shut the ignition off and the code usually clears upon restarting the vehicle.

The second issue are trouble codes, P0171, P0174, System too lean bank 1 and 2. Sometimes the vehicle will idle poorly on startup but smooth out when the engine iLs revved. Ive cleaned the MAF sensor, Cleaned the throttle body. 

Any input would be great, Thanks!

2004 Chevrolet Suburban, 340K miles