I don't fly EP so I can't be of much help as far as power systems, but as far as elevation goes, yes it does make a difference. What is the elevation you're trying to fly at?

As your elevation increases, so does the density altitude which is affected by the height above sea level (less dense the higher you go) and temperature. In basic terms, the warmer it is, the higher the altitude the airplane thinks it's flying at. So a plane that may fly good in Florida at sea level could be underpowered if you're flying at say 4000' - less air for the prop to bite and for the wings to develop lift.

Hogflyer