2003 2500hd 8.1l p0101 code

[KTMN8]

Truck is new to me. First trip out the 4wd message displayed, ignored it, then later it went into reduced power mode. Unplugged the mas, ran fine, bought a new mas, ran better than before, and 4wd message gone as well. Ran great for a couple of days, now down on power, and p0101 code keeps popping up. Also get p0650 for check engine light malfunction. Check engine light works intermittently. Checked connections to mas and Throttle body, seem fine. Not sure what to do next. The low end torque is way down. Feels like I have to push peddle farther than normal to get it moving. Oh, and the gas mileage sucks, but I’m sure that’s normal lol. Thanks. 

 

Also, I changed the plugs, wires, and fuel filter. 

[KTMN8]

Anything?

[sefiroxx]

9-10 mpg, normal.

MAS replaced, then either wiring problems or air leak along the intake. Does it run better with the new mas unplugged?

Bogged down. Lots of possibilities. Difference of manually opened vs peddle/cable? Works better on closed loop or open loop? Cat clogged? Air flow constrained? Fuel pressure low? TPS failing? Not all cylinders firing? Injector pulse width constrained by various sensor feedback (mas, temp, etc)