If you have TORS tune (and TORS + Cat delete) and remove secondaries you'll be running way too lean and will need a PC or Dobec (I have the Dobec) to rectify that. Definitly get a GiPro too and may as well get tripples while you're at it. In terms of bang for your buck, you can't better these mods. The GiPro may or may not make a difference - I think it does, but I did it at the same time as removing secondaries so couldn't say for sure - but you also get the gear indicator so it's worth it just for that anyway IMO. Certainly both mods made the throttle much much more responsive and smoother, especially at low speeds and I'd never reverse either, and I really notice the extra oomph when I crack it open.
I get 28 - 33 mpg depending how I ride; even close to 40 on the highway. Don't worry about using a bit more fuel; be more concerned about a/f mix. If a few extra bucks worries you then avoid not only the performance mods but maybe don't ride a Rocket at all.