carb issues
With so little to go on...
If you slowly roll into the throttle at cruise speeds and it just lays over, my bet is it's FAT.
If you roll back out a bit and it picks up, then lays down again as you feed throttle to it, that would almost confirm it's fat.
This is where an A/F meter would be a huge help. If you have no spacer on the intake, the three step jetting is likely making the cruise worse.