Have a 12.7 with a super 10 that I’m having issues with power once I hit 9th gear, it just struggles a lot after that, empty or loaded but it’s much noticeable loaded. Even empty on a small size hill it struggles. The other 12.7s I’ve owned weren’t like this. I’ve changed all filters, and no noticeable changes. Any other ideas where to start? Cac leak, or fuel restriction or maybe time to run an overhead? Just bought the truck not long ago, so don’t know when last time overhead was done. Any help is appreciated.