So what happens is whether the engine is running or simply in the 'on' position, and you try to turn the car off, either the power or both the power and engine (depending on what you turned on) keep running for about 30 seconds before shutting off. This happens consistently every time. It started yesterday after disconnecting the battery, installing an aftermarket stereo, and reconnecting the battery. I reinstalled the OEM radio to see if it made any difference and it has not. The car is completely stock. Did the gremlin check, no corrosion in the connections behind the driver's kick panel or any signs of water damage. Any help would be appreciated!

 

Sounds like a literal ticking time bomb!

 

It's probably got an aftermarket turbo timer in the car somewhere.

 

+1 for turbo timer.

 

first thing i thought from the title, turbo timer.

 

Look at the ignition switch harness. The Black/White wire should be interrupted. Follow those wires and you'll find the turbo timer. It's a good thing to have to let the turbo slow down and be lubricated before engine shut down. Mine is integrated with my alarm system and is set for 1 minute.

 

If your turbo is stock, or otherwise still water cooled, you don't reeeeally need a turbo timer. If T3 etc, with no water lines, then it's not a bad idea.

 

Found it! Thanks all.