HELP. I am working on making my nieces Mustang road worthy for her 16th bday. The tach does not work..the check engine light does not come on for a bulb check or anytime. I am unable to pull codes with a code reader or a snap on scanner. It says no communication. I replaced the ecu with a known good one and nothing changed. The main issue is that the car runs nice cold but after running for a few minutes (like once it gets in closed loop) it runs poor. Shakes and in gear (automatic) it runs rough. Any help would be appreciated. Powershift@comcast.net