Well put a whole new short block (the 427) in with same heads, manifold, cam and complete new exhaust system. No change in odor.

I have Mobil and Chevron Credit cards so that is the only gas it has seen. I have a full tank now but I'll try a different brand next fill up. I'll let Ya all know and thanks for the tips.

Speaking of exhaust, I put on 40" Thrush glass packs and I love the deep "Old school" sound without it being too loud. It has a nice low rumble while cruising along instead of the hollow tinny sound typical of the now popular Flow Master or Turbo type.