harbone,headres are matched set, all four tubes glow. and i cant find a vac. leak. even with this problem my son pulled the frontend skywards.!! in the driveway yet.well not that high but it was at least a good 8 inches off the ground.but after runnin for about 3 or 4 min. this thing starts to glow.i know its something small but its drivin me nuts, and i dont need no help for that.lol, the main reason i never checked the intake for leaks is because it runs so damn good.i have thought about putting a single 4 barrel intake on it and changing carbs around to see if that would change anything.but damn thats alot of work for a guy that cant stay bent over very long.after doing some thinkin about it i dont see how it could be 1 carb.sittin on a open plenum intake.