[Walt Fricke]

Dom - petrol not a good sign, as you recognize. Some pictures would be helpful, as not everyone uses the same terms for the bits and pieces.

The thing with an electrical connection I tend to call the auxiliary air slide - the thing you bench test by looking through it at room temperature, and after applying power to its heater, then putting in a freezer for a while and looking again to see if moves from open to closed and back again. I am dubious that the heater would ignite petrol, but best not to test that, and it shouldn't be there anyway.

A bit hard to see how petrol from the air box would get into the air plumbing. The cold start valve would be about the only source unless you have an intake valve which doesn't close, so compression could cause the continuously injected petrol to move backward?

Does the thermo-time switch, which controls to an extent the cold start valve, work as it should?

Did (or can you) you do a leakdown test on each cylinder? Or just do a compression test (might be hard to do on the engine stand, though).