1990 GQ, TB42 on petrol and gas. I'll start it from cold, on gas, it will start fine and idle correctly. Once I start driving and let it coast, the revs will drop out and it will stall. Once it's warmed up I'll switch it over to petrol and it does the same thing, idles correctly until I drive off and I'm up to speed or going on a downhill, let it coast and the revs drop and it will stall. Not sure if anyone has had a similar issue or not. Temporary fix has been winding up the hand throttle and a lot of left foot braking but is obviously a pain in the neck,. Any help appreciated