Hi everyone! the last couple weeks my truck has been acting funny. It seems to hang between 3-4 and the 4-5 shifts. If I watch the rail pressure on my cts it sometimes drops as low as 4.5k lbs, but it never throws a code. I rebuilt the filer head last week and now it seems to build pressure better, but then just falls off. At first I thought it was defueling real bad, but it does it even at 1/2 throttle in my 40hp tune. what could be causing it? It is random it doesn't do it every time