[Jack21]

Agree you may be pumping too much heat into exhaust from retarded timing, overly rich fuel mixture.

I use stainless fastners (nuts & bolts) on the header to "J" pipe and re-use them. No failures or loosning of fastners. Non-stainless split or star washers prevent fastners from heat stress or vibration loosning, but must be replaced when re-assembling. Most True Value hardware stores carry these. For really hard to find items, go to McMaster-Carr on-line (mcmaster.com).