Troubleshooting Help! Steady high idle

[ROMITON1]

I have the following engine mods:

UR FMIC, UIC/LIC, UR long down pipe, UR mini muffler test pipe, UR mini muffler CBE

I just had an SST transmission service done (problem existed before service as well). Car has 50K

When I go WOT (sport or normal mode) in automatic mode, the car will linger at redline for a brief moment. When I go to stop at say a redlight immediately after, the rpm will idle high at ~1800, it is a perfectly steady high idle though. If I turn the car off and back on it will resume the normal ~600 idle.

The check engine light will come on when this happens, but will disappear after a few days. I am taking it to a stealerhip, but they are being very finicky about my mods. Unfortunately I am new to Ohio and do not know any dealerships here, where as back in Texas I was in good with the service manager at my local stealership.