I just bought a 2003 mustang gt three weeks ago and I have been chasing an electrical gremlin. the person before had spliced in a custom alarm system and I found the tail light fuse was blown. some of the things that I have noticed is when the car warms up the battery light comes on. had the battery and alternator checked and they were working perfectly. did a parasitic draw test and everything was good. then used light probe attached the clip to the positive and probe to positive wire. it lit up so I know I have a short when the brake is pressed it strobes. then when the ecu fuse is pulled it goes out and same with pcm. I can deal with the light being on but it has a horrible miss when under load at low rpm and the shifts are very delayed. also when you come to a stop light the idle bounces up and down. also if the car is put in reverse without gas peddle being pressed the car dies but this is only when the battery light is on. please help I am stumped