I'm sure someone much more knowledgeable than me will come along shortly, but can I ask a couple of questions?. What type gas are You using,(octane), and could it be possible You have some carbon buildup?. Maybe time for a little Marvel Mystery Oil.

"All right, they're on our left, they're on our right, they're in front of
us, they're behind us...they can't get away this time"

Lt Gen. Lewis B."Chesty" Puller, USMC