My first thought would be something electrical - condensor on conventional, or a cheap Accuspark/Powerspark unit.
Second would be fuel starvation - what's the inside of your tank like? Fairly easy to take a peak. On mine, it had been lined at some point and the e10 fuel had broken down the lining and it would block the fuel pick up in the tank. Once I'd stop, a little fuel would flow back down the pipe, clear the blockage and it would be OK for a while.
May suggest why you can't replicate on the problem while running on the drive - although you're getting the heat into the electrics, you're not getting the same demand for fuel as you would be running out on the road.
Agree with the other checks mentioned - fuel filler cap breather, and ballast resistor wiring (I removed mine and replaced coil with a non ballast type with direct 12V feed.)
