GSX won't run past 4,500 on reserve

97 gsx. New fuel lines and new fuel selector. Carbs cleaned and rebuilt. Tank pulled and cleaned.

I've put about 12 hours on it and besides the rave valves sometimes acting up, it runs strong and will turn 6,600 rpms all day long but if I put the fuel selector on reserve, it won't run more than about 4,500 rpms before the motor wants to die. I think I got a bad fuel selector. Anyone else had this issue but it not be the fuel selector? Ideas?