Have a 600 com Edelbrock 1405 carb I am having some issues with. Any time I gradually bring up the rpms and then take my foot off of the gas pedal, it stays at whatever rpm it was at before taking my foot off the gas. I can then tap the gas pedal and the motor returns to idle. It is manual choke(which I have disabled and wired the linkage to keep the butterfly open). My question is what would cause this to happen, something internal? The only other thing I can think is that my return spring(spring that pulls the throttle against the idle adjusting screw when you take your foot off the gas) is not strong enough. Any ideas?