One other thing I thought of, when trying to get the manifold on or off, if you don't have enough clearance with the boxed in wrench as the nut is further away from its seated/tightened position, just slide the manifold away from the mounting surface a little (i.e. pull it so that it is up against the seat of the nut) and then you'll have clearance for the nut. Of course, to move the manifold, all of the other nuts would have to either be off or loosened to the same amount as the troubling center nut. If I had a pic handy, it would explain this better than words. Sorry... hope this makes sense. Easier shown that said.

 

Funny, mine didn't have that problem at ALL.

Glad you found a quick solution though.

 

+1
I have some Fujitsubo Ti Headers, came across the same problem and did what u suggested (before reading this) They say great minds think alike, or is it: gay minds, dick; I like . .?

 

I get my hardware from the local ACE or more often Mcmaster. Their new NJ ware house is 0.5 miles off my daily commute. Will call FTMFW.

Problem with allen head bolts (sockethead cap screw) is if they jam up, the allen head strip out easier than you can round a hex head. If you can find a torx bolt that'd be better. Or if you can find a 12 point nut you may be able to fit a smaller wrench on it. Maybe try Maryland Metrics

 

try the racheting wrenchs...they work like a charm. takes a tiny bit of fanagling to get it on there but I have taken the mani off and on tons of times with not problems. 14MM ratcheting box end from craftsmen. If I didnt use it I have no idea what I woulda done. try it before doing all the "hunting"