i wouldn't jump on getting that actuator just yet.
need to find out why the MIL light is coming on...
when the system detects a problem and turns on that light one of the first things it usualy does is put the system into limp mode, this is probably why your throttle actuator is locking into one position and not allowing acceleration.

gm v6 system eh?
does it have ECI system?
look on harness near ECM for a diagnostic connector, should be a 4 prong connector labeled A B C D.
you can jump terminals A & D and turn on ignition and get it to flash the stored codes on the MIL on the dash.
It will probably be in 3 digit codes
when first initiated it should flash like a 116 code to tell you the system is working, then a long pause and then the codes will start flashing. If more than one is there it will do the most prevalent one first and then graduate to the others, it should flash the codes 3 times each. Once it is done it will loop back and start over with the 116.
To clear the codes turn off the ignition and remove the main fuse or battery cable for at least 15 seconds. ( i would wait a bit longer just in case)
If any codes are persistent then you need to repair the problem before it will go away.

Once you figure out what the codes are you can come back and post them here and we can tell you what is wrong.

my guess though is since you replaced the pedal sensor you just don't have it set correctly.