About the throttle running on half and then it sounds like the rev limiter comes on.........My 400 did that one day after i was jumping this double over and over again then after i landed one time it wouldnt run right. It did the same thing you described. It ended up being that my air box boot from the end of the carb came loose and was leaking making it run lean on the top end. So then it would run great to mid throttle then you would try to give full throttle and it would fall on its face. So you might want to check the that?????????? Sorry but thats probably not it though.........