I crossed my fingers and used a u-joint/swivel, 3/8" socket, flex head ratchet, and about 2 feet of extensions. The drivers side and lower left nut came off easy enough, but the one on the top left was a pain because the socket slipped off twice on me. Once I repositioned the extensions and ran them up between two harnesses it gave me more of a straight shot and broke free.
Then just put the new bolts in from the top and bolt up the BBK pipes.
'13 Deep Impact Blue GT, auto, BBK cat deletes, GT-500 A/B's, C&L tuned DiabloSport inTune, sound tube delete, BBK 85mm TB, JLT oil separator, NX plate kit.