Output speed sensor circuit malfunction

My 01 gt auto just had a torque converter installed, and ever since ive had trouble with this check engine code (P0720- Output speed sensor circuit malfunction). The check engine light comes when i stall the car above 2000 rpms and launch or do a really nasty burnout. And when the light comes on the car bogs down to 3000 rpms, the overdrive light flashes on and off, and the odometer reads blank miles. This has only happenned to me at the drag stip. Does anybody know anything about this code? Or what i could do so that the light doesnt come on anymore and the car doesnt bog down? Thanks alot.

-70mm throttle body
-3500 stall converter
-SFC, LCA's
-Shorty headers, Full flowmaster exhaust system (x pipe)
-Hypertech power programmer (shifts programmed to 5800)
-4-10 gears
-MT street Et's
-KN air filter, oil filter

To tell you the truth, i cant find out where the sensor is hooked up, i thought it was on the output shaft of the trans but i couldnt find it anywhere. If you could tell me where it was, i could check it out, thanks a bunch.

Hey man thanks for the nice pics! Ill check it tomorrow and write back. Thanks!