I agree with TK, I had a coil issue that would simulate a carb problem at WOT. It would spit and sputter. A quick coil change (also inspect wire connections) can eliminate that from the equation.
You also noted a NEW carb? Did you install the original jets from the OEM carb into it? Those cheapy replacement carbs come with odd sized jets sometimes.
If you suspect a vacuum leak, spray around all mating surfaces of the intake/carb with starting fluid while running and see if you notice any RPM changes. That may help you identify a vacuum leak.
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My Yerban assault vehicle: 2.2mm stroker crank, 62mm Nikasil cyl, Taida large vavle head, American made valve springs, ported intake manifold, TM 28mm carb, stock CDI, Bando coil, TK exhaust, stock CVT except for the 14g sliders, 13/40 internal gears, 16T drive, 31T axle sprocket, 22" rear tires, and ONE BIG POTATO CANNON mounted on top..........
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