firstly you should never rev the engine and immediately switch off. sounds good but the press of the throttle puts petrol in the bores that then doesn't get burnt 'cos the ignition is off so no spark. the fuel washes oil off the bores so on restart the rings aren't lubed properly. lecture over :lol:.
so to the running on, how old is the engine? i mean how long since it was built/rebuilt not the year? it may have carbon build up on the valves, pistons and combustion chamber which will get hot enough to burn any fuel present after you switch off. this is made worse if you rev then switch off. you should know if it's too far advanced as the engine will be hard to turn over and may try to 'kick back' on the starter as the piston tries to fire. the plugs stop firing once you switch off so shouldn't affect running on anyway.
lastly does the car run on if you just switch off without revving first? if so i'd be inclined to go with carbon build up.
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