Sounds like you have a problem with your throttle linkage
and not the carb.
First off, does your radio should have some trim adjustments on
it. Make sure that the trim adjustment for the throttle/ brakes
is set to zero. If it is a knob type adjuster, turn it so the detent
is in the middle (+ I -).
Take the air filter off the carb, turn the radio on, turn the receiver
switch on. Is the carb slide going closed against the idle adjustment
screw now ? If not, you need to adjust the linkage going to the
carb. If it is way off, you may have to move the arm that connects
the linkage to the servo. If you do have to move the arm, make
sure you check to make sure that the splines on the servo and
inside of the arm aren't torn up.
If this takes care of your problem, make sure to cycle the servo
a few times each way (full throttle to full brake) to see if your
adjustments remain the same. If it looks like it has changed
vastly again, you may have a bad servo or arm. Don't attempt
to run the car until you correct the problem. Having your car
run away at full throttle always ends up costing you alot of
I hope I may have helped you out, good luck.