the truck is a 07 5.9 has a six inch straight exhaust. and a dropin filter and a diablo sport predator tuner otherwise its totallt stock. i took the tuner off the truck. when you free rev the truck as it comes back to idle it studders and sounds like its missing. with the tuner on it it will give it a odd idle sounds like a lope weird tone, but only with the tuner on it. whats causing it could it be a bad injector truck has 103k miles runs strong but the studder makes me nervous nw to the commonrail game. the rail pressure at idle is 6800+ peaks around 22k-24k