Hi Steve,
Funnily enough I've just re-fitted my std cans and the relevant Power Commander map and the bike feels no slower than when I had the race cans on there. In fact I'd say it feels better at the low end of the rev range.
However, I've not got a K&N on mine (not convinced they're that great, or flow significantly more than a new OEM filter), so I think the map I had for the race cans wasn't running quite right for me.
Ideally I need to get it on a dyno, I just haven't got around to it yet.
Let me know how you get on - we might be able to trade some maps with each other. Shame there's not more people using them - with other bikes there's a thriving community of people all trying different maps.
cheers,
Nik