LMM Turbo Brake

Looking for help with a 2008 LMM turbo brake. My tuner has been unable to get the vanes to close. I have verified that the DSP5 install is functional, using tow haul, tried manual downshifts, and towing a loaded trailer. Vanes do not close beyond 80%, and this is only for a split second. This particular truck has 130k, great power, 17 mpg mixed mileage, new CAC boots and clamps (system pressure tested for leaks), and vanes perform full sweep. Any help is appreciated.

I would make sure the max vane position, tables B2222 thru B2224, are set high enough for a start.