Ever since putting 2.02 camel humps on my 350, as I am cruising there is a slight surging in the engine. If I put my foot in it to give it load it is smooth as can be. Have done many different timing settings it is always the same reaction, I even put on a new vacuum canister. However, if I do not connect the vacuum advance the engine runs smoothly at any throttle setting, as soon as I hook up the vac canister it will surge. And yes, I have looked everywhere for a vac leak but I find nothing. Really stumped, but I think it has to be a simple solution.