When it idles the tach bounces from about 500-1500 rpm and then after about 10 minutes it dies, I can restart it but must give it gas to keep it running. No check engine light, I plugged the scanner up to it anyways and no codes, the fuel pump and fuel filter have about 10,000 miles on them. I did some research and thought that its probably the idle air by pass valve so I replaced it and it does the same thing. I recentely installed a built-up 306 (10.3:1 copmression ratio, F-303 cam, and some other goodies) it still has the speed density system with a Jet chip. Could the cam be too much for the computer to handle? Also last fall when the origional engine was still in the car it ran fine (except for the burning oil). If anyone has any ideas I would really appreciate it.