The last F&%ing manifold bolt!

Had a similiar problem with the rear driver's side header bolt. I hit it with penetrating oil, tapped it with a hammer and socket extension...nothing. Next heated it with a torch, then sprayed more penetrating oil as it cooled...the 12 point combo wrench (no room for a socket) started rounding off the head of the bolt. Picked up a 6 point combo wrench...heated the bolt with a torch again, spray penetrating oil, then was able to break it loose. Needed to use a piece of square pipe over the combo wrench for leverage but got her loose. Note: this bolt was hit, heated and soaked with penetrating oil for 2 weeks before it finally gave in to me. Good luck and do not force it, definitely do not want to break that bolt off.

Pat