Hi guys, need some help. I have a recently rebuilt 302 (1500 miles) with edelbrock performer rpm carb 750cfm (electric choke) performer rpm intake and performer rpm cam. Cast iron heads with 1.9 intake and 1.6 valves. roller rockers etc. I had the car on the dyno did 300hp at 4900rpm. Rev any higher and it just went dead. timming was advanced but it did not help. We suspected a ignition/ distributer problem took the car to a distributer guy who replaced the module (stock ford distributer with ignitor electronic conversion) and he also replaced the coil. This did not help.. I took th car to another mechanic who asked if I had replaced the valve springs when i did the engine. bingo... i did not! so he repaced the valve springs with Isky double springs for high RPM performance. I get the car back and now it revs to 6500rpm but at 2500rpm when "under load" it misfires. take your foot off and accelerate slowly and its fine. it only misfires at this rpm. need help as i dont know why this is now happening, as it was not an issue before.. I have taken it back to him and he has reset the tappets and is now blaming the distributer. I am going around in circles!