Engine/Transmission (1998.5 - 2002) miss at idle, where's my cloud?

[Cummins724]

I have a 99 [5speed] truck with 130,000 miles & lately have noticed a wierd miss while idling. When driving I've noticed that with my comp on any setting, it don't blow that soot cloud that it did before the problem. I spoke to a mechanic & he said it may be the map sensor, but he is not sure. It just don't have the spunk it did before either, but yet no codes on the scanner. Truck has Upgraded fuel system 14 psi. @wot. 90hp injectors, gauges, 4 inch exhaust, intake, everything has been on this truck for last 50,000 miles. any info would help please!