the os 18 is nearly too much power anyway, imo. the .28 is ridiculous - trust me mate, its a lot of hassle and breaks stock parts very easily.

i have the os.18cvr-x as well as an sh.28 in my funfactors. the .18 is brilliant, use the cen stock clutch and flywheel, just make sure u get the rotary carb version, the slide carb is a bit harder to set the linkage up for.

as for a pipe - i am running the os t-1030 alloy tuned pipe. no complaints there, and it gives a fair bit more poke than the stock cen plastic pipe. i run it on 25% nitro with an os #8 plug.

its by far the best engine u can fit to a funfactor. it will wear parts quicker than the stock motor, obviously, but it wont wreck them as soon as u punch the throttle, just be a little careful with the throttle control to lengthen parts lives.

is he just after ur $$$ tho?