I recently got a Benelli M2 12 gauge tactical semiauto with the comfortech stock (legal in NJ).  I've only shot birdshot at the range so far.  The gun came with several chokes.  I got a goot deal on Federal Truball rifled 2 3/4 slugs.  Which choke should I use for the slugs?

The general consensus is that IC works best.  Technically you can use any choke you want but it would be silly to force a big honking wad of lead through a full choke.  You could also go with Cyl but you may get some blow by. 

TruBall's are unique in their design, different than Foster's, because they obturate differently in the bore upon firing due to different wad construction and Federal's little plastic ball behind the slug. If you have CYL or ImpCyl choke tubes, you're fine. I would test fire for groups with both. One independent range test proved IC worked the best, followed by CYL chokes. Your results may vary because no two guns are alike.