Not that anyone should have been under there to install a throttle body (unless they thought you said Valve Body)
but make sure the return spring is installed (Driver's side) on the outside of the trans.
Also your kick-down linkage adjustment is touchy.
It has to move
as soon as your throttle does. Not before (so not under tension), not after.
Another touch adjustment (can be) the BBK curb-idle adjustment. If it is open too far, or not far enough, it will go to war with the A.I.C. motor to try to keep the idle level. It is a trial ad error adjustment and it is also very touch. SMALL adjustments either way will/can make a difference.
Apparently all the schools are closed here in Calgary Alberta until September and we are under state of emergency so I better stick my head outside and shine up the 50 cal.