87 S4 Ignition Problem
 

I am having an intermittent problem when turning the ignition off, about 50% of the time the engine stops the other 50% it just continues running and I have to either stall it out or quickly flick the ignition back to start and then off. I have removed the turbo timer and it was not the problem. The car has been modified with the starter relay mod, before that I was getting the click click when trying to start.
The car is a JDM 87 turbo.
Hopefully someone has some good suggestions for trouble shooting. Thanks
https://cimg1.ibsrv.net/gimg/www.rx7...d89bb0ae66.jpg

pic of the car

When did you start having this problem? Was it after the starter relay mod? If so, than I would suspect that the mod is the problem. If not, than I would suspect that the ignition switch harness (https://www.rockauto.com/en/moreinfo...192340&jsn=356) is the problem.

I didn't notice the problem when I bought it, but I did the relay mod just after I bought it. I will have a look at the ignition switch harness, is it possible that there is a sticking relay in the start circuit that does not release some times?

Other than the starter cut relay (which is NC), is relay in mod that you've done (which is NO).