FWTW - I heard that not adding a fuelpack (or doing a fuel mapping download) might increase the amount of snap, crackle, and pops you get while riding - but nothing too crazy.

I also have Vance and Hines SS on my Iron. When you eventually decide to go with a fuel pack, I recommend the dynojet power commander along with a big sucker air filter. I pretty happy with how both my exhaust sounds and the added performance while riding (the bike breathes so much easier at 3,000+ RPMs now) - given I eat up fuel faster now.