a couple guys mentioned fuel pressure, i think 7 lbs is just about right for carbeurated (getting old and barely remember carbs). Too much fuel pressure can act the same as too little fuel pressure fyi. (breaking up on high rpms.) it will also cause probs in the acc. pump. another thing, actually check your fuel lines, if they are old and cracked they could be sucking air at higher rpms causing the car to go lean. (assuming you have rubber fuel lines part of the way like most people)