As suggested, I'd shoot some dove shot thru the choke to break it in, as well as making sure your POI is correct. In my 2-3/4" Browning A5, 21" Invector Plus, I've gotten a max count in the low 160's w/ Hevi-13 #6 (1.5oz) thru both a Kicks 670 and 680. My best patterns come with a "Deep Cleaned" bore with about 3 or 4 shots through it. I haven't shot the IC 675, but with the IC 665 I've gotten in the upper 150's with that choke on the two patterns I've shot with the Hevi-13 #6.
Good luck.