I wonder what was wrong with my +4 motor

Well I don't know how to explain this but it like full tank lean bog problem.
but it flamed which is very bad for racing when you flamed after every pit stop.
It just happen lately. Right now I have to richen my lsn almost 3/4 of a turn to compensate which is really bad for milleage from 10 min drop to 7:30

I use OD 97T plug 25% nitro
80 degree air temp with 80+% humidity sea level
lsn is quarter of a turn out from flush (as rich as possible set without flooding the motor)
hsn is almost flush
my motor temp around 220-230 when tank empty.