bought this machine used at the end of summer, about 500 miles on it. seemed pretty good and i could get about 45 mph out of it. then the timing belt tensioner blew apart, had a new tensioner and belt installed, seemed pretty bagged out after that, then the head gasket went and the valves were found to be out of spec. got that all fixed and it seems even more baffed. the top is 24 mph and although it sounds ok, it still seems to be struggling. can anyone help to explain this power loss?