Anyone know how to change engine attributes in a TURBOPROP in fs9?

I'm interested in modifying my B200 King Air to Raisbeck, Enhance Aviation, or Blackhawk PT6A-52 type engine conversion specs - I was looking at the aircraft.cfg file though and unfortunately it's not as easy as it is to modify a piston engine aircraft in FS9. Does anyone have any experience with this?What needs to change is that the engines need to be able to develop full power up to 27,000 feet rather than 23000ish feet like the stock 200 can do. The actual output of the engines doesn't change, but their max power is available to a higher altitude.