I really don't remember my 275's adding anything noticable to the EGT's. I do have the Quad Monstor air box on mine. You might try drilling holes in the bottom of your stock box, or get an aftermarket box to add more air. If you still can't keep them under control, you could always add water injection.

 

Dad has that set up, 275's (300's) and a ez, and he tows all the time with no egt problems at all. 1300 max