It seems normal to me. The stock header glows red with consitancy. Exhaust gases get extremly hot. I don't think you have a promblem. Just check it over and see if you have any promblems.
Edit: I didn't read all that you wrote. That does seem odd that the peice that changes from 4 into one glows red. You must have some kind of restriction right around that area.
Edit: I didn't read all that you wrote. That does seem odd that the peice that changes from 4 into one glows red. You must have some kind of restriction right around that area.