should be easy to identify, look at the right side of this page for standard bolt heads.
http://en.wikipedia.org/wiki/Torx I'd guess Torx, that's what they used on the MAF, but just take a look, easy to tell the difference. If it is Torx, make sure to note whether there is a pin in the center of the bolt or not, or just get the Torx bit with the hole to be safe.
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'99 GTP, L36 bottom, XP cam, Headers, 3.29 gears, FWI, Powrtuner