the only catch with the vice grips on the protruding nub is the fact that its nesteled quite comfortably between the intake plenum and the head... the girth of the Vice grips may not fit or be able to turn in order to unscrew that portion.

IIRC, its a 8mm x 1.5 bolt. im pretty sure you can find the helicoil kits at Discount Auto if worse gets to worst.

you should be able to ease-it-out with an Easy out... just make sure you center punch the broken bolt and put a nice dimple in the top... otherwise, if you try to drill it w/o the dimple, the drill bit will skate around till it finds a low spot, which may or may NOT be directly in the center of the bolt... if you end up drilling off center, there is a good chance that the bolt and the head will be damaged.

like they said, besure to get the Easy out w/ the reverse threads, not the 4-sided/hammer-in Easyout. dont forget your WD-40/PB blaster.