Jdog,
I believe what you were driving at is weather the combined horsepower may be used to qualify as high performance, or weather each engine must exceed 200 hp. Is this correct?
The ratings of the engines cannot be combined to come up with that figure. In other words, if the power of each engine is 180 hp, then the airplane is not a 360 hp airplane that qualifies. It's a 180 hp airplane that does not qualify.
14 CFR 61.31(f)(1) specifically states "...(an airplane with an engine of more than 200 horsepower)..." when defining High Performance. Had the rule made allowance to combine the horsepower ratings, the wording would have been "an airplane with more than 200 horsepower." However, it doesn't say that. It specifically identifies the requirement for an engine, in the singular, or more than 200 hp. In theory, this could be accomplished by having only one engine that exceeded this rating...one 180 hp engine and one 200 hp engine, for example. That's a little far fetched, but for illustrative purposes, only one engine must have that rating.