questions about a Cummins ISM turbo

[Bearmtnmartin]

Hi all, I put the driveline from a 2000 Freightliner Century into my 1981 Bluebird Wanderlodge RV. The motor is supposed to be an ISM but the valve cover says M11. Engine model as per the ECM is an ISM500 rated at 425 hp. Serial number is 34963313. So I am confused as to what I actually have. The turbo is not wastegated but most of what I read says the ISM's came with a wastegated turbo. And since there is no wastegate how is boost limited? The reason I am wondering is I am down a little on power. Boost comes in late and slow and will only build to about 27 pounds. I have pressure tested the CAC and piping and it will hold 25 pounds. I have no codes other than low coolant and everything was new when I did the repower. I have new injectors, a new turbo (not chinese) a valve set and filters and oil are good. Just looking to get all the horsepower I can after i did a lot of work to get here. Thanks for the help.