Re: Mopers comments about the step-up spring. Do the other stuff first, as getting the initial right and getting the carb working right will have a BIG effect on the manifold vaccum. ONCE this is all done, if there is STILL not enough vaccum to hold the power piston down against the spring, THEN you need to look at messing with the step-up spring. Just swapping the spring out may get the metering rods down in the jets, but the manifold vaccum will go up, it'll have more bottom end, & get better gas mileage if its set up properly.