i came outside to let my truck warm up. fired right up. let it warm up a good while since i havent drove it in a few days. 30 minutes later i go to leave and i reved it twice to 1500 rpms cause i love my new exhaust. after the second rev it died. tried to start it and it would just turn over. then i had to give it pedal to start. held it at 1k rpms for a few seconds. sounded fine and everything. let off the pedal and would die right away. then tried again and it still is happening. what is causing this?