CM2350 bad delete

[jwt41]

I had my CM2350 demandated about a year ago, and it has not been right since. I went through 2 turbo's before deciding to add a compound turbo with the VGT. Fuel mileage and power both went down, except in low altitude it runs good but fuel mileage is still bad. I took it back to the same shop because of the poor tune and they cannot figure out how to tune it with the compound turbo being added. I am at my witts end and afraid I may do serious engine damage if I do not get something done. I have no experience with Cummins Insite, or Calterm, if I had known about this forum prior I would not have taken this path. Any advice is appreciated!