When you replaced the ACC Pedal... Did you use either an ACDelco or Delphi OEM Replacement Part...or did you choose an Off Brand or After-market Component? This choice may make ALL of the difference in whether or not it works well with the PCM in a compatible way; given the sensitive nature of the Dual High-Low 5 Volt variances used to calculate Pedal Position accurately via Pulse Width Modulation (PWM) on the Class 2 Network.
Also... Chafed, Broken and Shorted wires hidden inside of Wire Bundles or in/near Metri-Pak Weather-Proof Plugs that connect up the The MAF Sensor, The Throttle Body and The ACC Pedal; all and sundry, if shorted or damaged can cause the PCM to place the Engine in Reduced Power Mode instantly if
ANY of them suffer Poor Plug Connections or Broken or Sketchy Wiring.
Be suspicious ...Use a Bright Flashlight and a Light Touch when performing any "Push-Pull" Wire Harness and Plug Testing around the Engine. An inexpensive "Broken Wire Probe" Kit from Harbor Freight can be VERY useful in rapid, pin-point Broken Wire Tracing inside of harnesses as shown by Brian from Briansmobile1 using a less expensive variant in this Youtube Video:
...and here is another Video on the subject from Eric "O" over at South Main Auto discussing the "Power Probe" Variant of this Handy Tool: