mates just picked up a 2008 rxp, 67hrs, just had an x charger put on it, r&d air intake and a works grate. ( got the old charger too its fine)
wear ring is new, less then 1hr

has a slight issue it sometimes struggles too rev past 7000rpm.
it will some what surge down low, (4000rpm) and carry on abit but clears its self and will scream to read line, 8280 @ 71mph
charger is fine, hasnt dropped its washers.
air intake is, fine no water ingestion
nothing stuck in the grate/prop

the battry however often gives low 12volts warning how ever its still starts and runs, has had little use since jan this year so hoping abit of use will sort it out.
terminals how ever are clean and done up tight.

any ideas? im leaning towards dirty electrical connections, spark plugs are also on the list with abit of corrosion around them

any suggestions would be great cheers!