I have a '32 ford w/a 350 GM performance parts crate motor. The builder put on a Offy tri-power package but it's only running on the center carb. There's a plate on the 1st and 3rd carb base plus the fuel line is blocked off. I want to run all three but the idle drops down while in gear at a stop and I want to get that fixed before dealing with the other carbs. Everything is fairly new. I've replaced and tested all hoses for vacumn leaks, tried adjusting the fast idle and air/fuel mix screws. Even tested with starter fluid on all possible places for a leak. Carbs look brand new so I don't think they need to be rebuilt. The carbs are rochester GM 2 Jet, center carb is a manual choke. Any other suggestions?