Ignition and Idling problem still

[1995gtStang]

1995 Mustang GT 96,000 miles
Previously I had just an idling problem.... I would be at a complete stop... press the gas... it'd idle to about 500-600 rpms and almost die then surge to where it should have been in the first place.

I suspected the IAC Valve and Gasket... removed from the throttle body down to the air filter and cleaned everything I could. The springs in the IAC Valve where gunked up and mild to rough carbon build up came out in chunks after cleaning. The gasket was okay but replaced it anyway. After it all dried (cleaning solution) I put it all back together and reinstalled on the engine.

I started it up and it ran fine for about 15 minutes and then it died on me... at which point I tried to turn the key off and it was able to be pulled out but all the accesories were still on so I started it up again with no problem and I was then able to remove the key completely and the engine still ran. I'm going to replace the ignition switch and lock cylinder soon cuz I think that's the problem but anyone else have any ideas on this or the idling problem?

I will probably clean the egr and see if the egr slot into the intake is clogged. Also heard it might be a fuel pump problem. Also tried with the error KOEO and KOER tests but since I can't turn my engine off with the key it's kinda hard to set up for those tests in the first place. Any help PLEASE!