Cummins ISM not reading boost correctly?

[Mikesuburban1]

Hi all i know you mostly talk about the isx but i figured someone on here could help me. Soo the truck is a 07 IH 7600 with ism@425hp no dpf. New turbo new egr, manifold pressure sensor, intake temp sensor, egr temp sensor. All new parts have maybe 1000 miles on them. Now the truck is sluggish my scangauge reads 31.5lbs boost but my mechanical gauge reads 35-38lbs boost but once in a while the computer will read 38lbs and the truck pulls like it should but then goes back to 31.5lbs. What can be causing this? It has a new manifold pressure sensor could it possible be a ecm problem? Any advise would be much appreciated [/size]