I have a 1993 6.5L in a 1983 Chevy crew cab with a NV4500 behind it and it has a cold air intake and 4" exhaust with a 3" town tube. My issue is I put a Heaths Diesel boost controller on it and can only get my boost up to 12PSI with it spun to the moon. I was told that these motors can handle up to 15PSI. Any suggestions on why I am not building boost? At what I would consider normal high RPM's it is around 8-9 PSI.