I installed the 93 octane evolution tune with c&l intake a month ago, and every since it was installed the car makes a funny sound when the ignition is turned off. It goes "pssst" like a piston turns once more but doesnt fire?? I dont know if that makes since..

any suggestions?

 

Completely normal. This is just the sound of the air backing out of the filter. Remember you now have nothing covering that filter so you hear everything.