I had my cans cored by Baines racing on my old 996, they set up the fueling for the free flow cans and it ran fine, standard look but you get the proper noise (it was as loud as any race cans)
I don't think I'd go that route again though as you don't have any standard cans to put on if they do clampdown on loud cans or can't find a friendly MOT station, better to buy some second hand cans off the board or ebay (thats what I did this time
) also if you do ever sell the bike you have standard cans to put back on and you can sell the race cans on, most dealers won't want a px without standard cans and most private buyers are the same.
Darren