DBW Throttle acting funky

Now I've got a throttle body problem. it is odd. I can turn the key to the on position. press the throttle, and you can hear it open and close. I start it, and it'll start fine. Then I can press the throttle for a few seconds and it will rev. then the pedal goes dead. no throttle response at all. it just idles. no more, no less. just idles.
2003 5.3 and 4l60e LS Swapped into an '86 C20 pickup.
Ran poor, with all four gears in the 60e trans.
ran good, with 2 gears in the trans cause of a bad 2-3 shift wire and a replaced exhast gasket
now it doesn't go off idle without dying. it'll putt around at idle, and if you go SLOWLY onto the gas, and I mean SLOWLY, it'll get up to speed. but it has all 4 gears!
Could this be a battery problem? The truck had sat before this for a while, and something drained it pretty dang good. took several minutes for me to be able to start it with jumper cables on it.
If you gas it hard and then will only idle, it's probably in limp mode. That usually requires a battery disconnect to get back any throttle response. The code will help tell if it's the TAC, pedal, or wiring.



