I am sure by now everyone here knows I've been inducing HHO to my 1985 300SD. I know the question I am about to ask I'll get a lot of heat from asking it. but that's okay that's why I am here to get to know this car.

Anyway, I decided to increase the gas production on the generator onboard, from 1.5 lpm to 2.5lpm. The engine accepted it with great result both mileage, power and how the engine runs (at idle the engine barely shakes) even the air cleaner does not shake. the one thing that was noticable was the "post shutdown". The engine still runs for about a second or two.

What does that means when it does that? How can I prevent that?