glowing spark plugs

The motor is an older crate 360, the carb was running lean a few weeks ago. Gotit off ebay, it is a 750 w/ vac secondaries. It had #63 jets with a pluged power valve which did cause it to run lean. as I said a few weeks ago I changed it to #73 jets and a 3.5 power valve to fit my 7 in. of vac. I can not find any vac leaks. I do hear what sounds like an exhaust leak on the driver side. the exhaust leak is what made me look at in in total darkness finding the whiteish glowing plugs.