Ok so I just put a head on this car. Used replacement. It runs GREAT for a little bit but then starts to load up stink like gas and run like it is missing very bad, also blowing smoke. Shut the car off for 5 minutes start it up again and it runs great for about 10 minutes or so then starts all over again. Where should I start now with this car? The bottom end only has 40000 and the head I was told low milage. All the sensors were replaced when I rebuilt this car the first time 40000 miles ago. The only thing never touched was computer??? and exhaust. PLEASE HELP IF YOU KNOW WHAT MAY BE GOING ON.