How about clogged/melted catalytic converter. If you run super rich or have a cylinder missing you can melt it. Run open exhaust can let you know if it's that one supper fast. That's a more gradual problem.
__________________
|RIP|6spd-sport|OSG-LSD|XP8|RBF600|Eibach Sways|RE-71R|FI-34Row|Gen3-CAI|Yaw P.S.|
|