Racing a Beneteau 331
There''s lots of stuff you can try, but in answer to your question about modifying the rig, it depends in part on whether you race using PHRF. If you modify your rig in a way that gives you a distinct advantage (add a larger main), chances are your rating would change with such modifications. Some racers take these changes gladly thinking that a reduced rating (greater handicap) is a worthwhile price to pay for greater boat speed, to have a better chance of being first to the best wind.
It depends, too, on how the boat is rigged already. Does it have a vang? decent downhaul, outhaul (sufficient purchase?)? Backstay tension adjuster? How new are your sails? How clean do you keep your bottom? (the boat''s, not yours). Do you fly a spinnaker? How about the prop? Fixed? Switching to a folding would again, probably change your PHRF rating, but it might be worth it.
There''s a lot of stuff you can consider doing to immprove racing performance, from ergonomic stuff (making it easier for crew to control sails by properly leading lines, providing the right equipement, etc.) to minimizing weight on board, and probably 20 things I can''t think of at the moment.