Stroker engine "diesels" after I shut it down

as others have mentioned it could be a timing issue.....but to step outside the box I will mention a couple other things.

normally when I have had this happen (on any engine for that matter) its a problem with current in the system back feeding. more often than not I find it to be faulty wiring on an electric fan ...as the fan spins after the engine has shut down and back feeds current through the system almost like a generator causing ignition.

if you have an electric fan, try disconnecting it and then starting the car and turning the ignition off and see if the problem still exists.

also if you do not have an e-fan, try disconnecting the alternator wiring and doing the same process as it can cause the same problems some times. After you are able to pin point what is causing the problem,you can then work on the solution.