Excellent photos and write-up
. I went through setting up the same stuff DIY, and everything you've posted here lines up well with what I've observed also. I'd especially like to emphasize what your mechanic said about driver vs passenger side. If you find yourself having a real hard time getting at the passenger side bolts - just forget it and have someone else do the work. The driver's side makes the passenger side look like a cakewalk. The headers making the crossmember clearance worse is interesting new information, I guess that explains why I had the most problems (my headers and cats went on before the catback, whereas everyone else has done it the other way around).