He's at 9000ft, stock pressure will not be 150psi - thats a stock number for sealevel. I don't know the ratio, but %30 loss doesn't sound out of range for that altitude. You probably don't need a new top end (pressure difference between the cylinders is within range), but you probably do need to get a high compression head for it to run well at that altitude and find someone with experience tuning carbs for that altitude to help you out with the tune.