[shakewell]

It could be a lot of things, but from what you're describing it might be a leaky fuel injector. If that's what's going on, the injector is pooling gas onto one of the cylinders after you shut off the engine (flooding it until it gets cleared out) because the residual fuel pressure wants to go somewhere.

Here's what ya do to check it: Connect a fuel pressure guage - hopefully you have a schrader valve on the fuel rail - otherwise you'll have to use adapters at the fuel filter to connnect it. Check the fuel pressure while the engine is running.
While you're at it, make sure the pressure is within spec. Shut off the engine and watch the fuel pressure. If it drops significantly within ten minutes or so, then you probably have a leaky fuel injector.

I'm not saying that this is your problem, I'm just letting you know how to diagnose the problem you think it is.