the red hot header pipes ive seen was on cars with c. converters. if the car ran rich the gas would collect at the inlet of the conv. and burn the excess fuel up. a lot of the ford cars header pipes would run red hot at the conv. and catch the grass on fire. with open headers ive never seen them get red at the collector, but if you get enough gas in there i guess it could. i belive it would show up as a rich exhaust first. i had a lot of them run red at the or just off of the head from being lean. i ran blowers on the st. every day for 15 yrs and one thing i learned is you're better off rich than lean. if i was gonna do it again id look into the o2 sensor that you can put into the exhaust pipe with a light inside the car that will tell you if you are lean or not, if that works sure would have saved me a lot of money, you said you didnt have but 10 in. vac. thats not enough. do you have power brakes?