It's impossible to give specs to suit everyone.
Some people want rev-o-matic top end monsters, other want tree stump pulling torque fiends. If I gave one spec, I'd have to give them all. And I don' know them all, so I can't. Also, no way am I opening myself up to some dumbass US litigation because of hamfisted use of a bastard file! Your best bet is to get one the Gurus to do a tune. Harry Barlow, Farron etc are damned experienced at this and do good jobs. It's their business! If you fit K&Ns or Ramair individual filters, fit extension tubes between then and the carb mouth. This tunes out a horrific midrange flat spot that would otherwise occur due to pulse effects reflecting from the closed end of the filter. Don't forget to up your jet sizes as well, otherwise it's bye bye engine. Expansion pipes look better than standard (IMO) and help the engine breath better, although you will probably lose some of that lovely mid-range torque on the 400s. Again watch out for rejetting.