Car goes to idle at speed

[luggss]

I have a 91 civic hb with a swaped in sohc 1.6L ZC. At a stand still the engine runs fine, It idles and revs up to the rev limiter with not problem. Oh ya i race it on a oval track. At pace speed its fine with short bursts (30-50 km) When its go time i mash the gas it boggs and sputters and then goes to idle. ive tried to ease in to it its ok but when it gets to a surtan speed? (no speedo) it goes to idle. i restart the car and all if fine. till its go time again. Any help would be great. Thanks

Optional Information:
Year: 1991
Make: Honda
Model: Civic hb
Engine: 1.6 ZC

Already Tried:
ecu pr4 runs it ok and dont shut down but rev limit is to low. pm7 ecu shuts down pm6 shuts dowm pr4 with rev chip shuts down

 

[civichatch1988]

Is your ecu throwing any codes? Could be ur IACV, or maybe timming those are my best guesses. May also wanna check vacuums and such