The Pilot of an experimental single engine declared an emergency and diverted to a nearby airport when the engine began to run rough and lose power over mountainous terrain. The pilot and his passenger landed safely.

Narrative

Climbout was normal but when almost at planned cruise of 10;500 FT the engine coughed and started to run very rough. I immediately turned around and headed via the highway below towards ZZZ; in case a total engine failure occurred. I called ATC and declared an emergency in case I had to land on the highway and needed assistance. There was a TFR off to my left about 1 mile (I am not sure if active; but it showed on my GPS) of about 1 mile diameter close to my path; I assume for a forest fire watch. I came close but don't think I entered the TFR. I had difficulty maintaining level altitude and was worried about losing the engine so I came close to minimize the distance to the airport.I made it over ZZZ with some altitude to spare. The approach and landing were normal with a good touchdown. We tied the airplane down and departed with the local Sheriff's department; who responded. The airplane is currently under investigation by an A&P; and it looks like it was a combination of a restricted injector nozzle on 1 cylinder and a magneto failure.