Holleys are not too hard to work on. They have idle screws in the side of the front metering block. They are notorious for blown power valves. That would describe how yours is running. Also adjust the float level. Just take the sight bolt out of the side and gas should just barely come out. Do both front and back. Then I would adjust the idle screws. They should adjust to a nice tune. The power valve is accessed in the back bowl. Remove the four bolts that hold the rear bowl on. Take the bottom bolt off first and catch the fuel. Then remove the bowl. The power valve is unbolted using an adjustable wrench. Then just replace and bolt the bowl back on. Also use a little petrolium jelly on the fuel tube "O" rings when pushing the bowl back on. I'm assuming its a 600 vac. sec? If you buy a power valve I'd just buy a carb kit. That way if you break a gasket you could replace it. Good luck and let me know how it works out. If you have any questions I'm here.