Now that you mention it, I did have the same thing happen to me at one of my very first races in the GT40 when I was still setting it up. I had been idling for way too long in the queue for a 1/2 mile sprint on a warm day, and when I when to pull away it was like the fuel pump was playing up - a horrible run.
I added a 1" phenolic (?) spacer under the carb, and this wonderful insulation around all fuel lines around the engine (I LOVE this stuff). Solved all the problems.