Hot slot intake manifold

[68Gold/white]

I've used 1/4" pipe plugs, cut off the ends of 3/8" bolts and bought 3/8" set screws

You really need to plug those holes. It's old technology. Trying to heat up the carb base for better fuel atomization, especially in cold weather. The exhaust gases erode the base gasket (even the correct one), and make a vacuum leak. If you thick base gasket didn't have that gap forward of the 2 primary holes, it might work...