Good point Geezatec, I'll try a different Plug. It is hot in SA now as we are going towards the end of our summer and we are running at high altitude as well. I normally run the No6 plug.

Im running the S733. I'm only having this issue with this motor in the car. I've had a nova 353 and n12t1 in it with no problems. I'm also running a long line from the pipe to the tank to try and keep the pressure constant.