Im sorry, I meant engines, like 2 strokes and 4's. What I would want done is similar to what AB Mods does to RC engines and my engine for my RC8 FT is on the way to him now, Im asking this because for example if a plane requires a 61 2 strk but I want more power like the power of a 75 but wont fit In the cowl I can have it worked on to get .75 power out of a .61 for example. Thanks again and sorry for not being clear, my fault.