lol.  just go in ur planes  .config file, look for ur engine parameters, and change them from the captain sim norm of 60100 static thrust. captain sim for some reason puts all their boeing addons at the lower end of the specific planes engine rating thrust.  However, I go to wiki, look up the exact engines for the specific model boeing aircraft, and I set the static thrust accordingly to the highest rated model engine I find that is currently in service with the boeing jet. So then I put my engines around 65000 static thrust (which is on the top end of PW and GE engine ratings for 767-300) and i have no problems getting to any altitute under 40k. its quite nice now.  Very simple fix!