After truck has sat a few hours and I proceed to accelerate from a dead stop, I can hear a flutter /miss sound coming through the exhaust. When this is happening, the truck feels very sluggish as if a choke was on. Then around 40mph, the motor tends to kick in and starts running fine. The sluggish feel and flutter sound seems to go away.

In the past 4 months, I've replaced all plugs, fuel filter, oil, exhaust manifold, both cam phasers, replaced transmission fluid, cleaned MAF sensor, throttle body and have had Flowmaster single in/dual out exhaust installed. Once the truck has been running awhile, the problems seem to go away until it sit again. Please help!