Mick mine came with Ramair filters on it when i got it.
The guy i bought if off (good friend) had never done anything to the carbs and it had had those filters on when he bought it.
By the way it has standard CV's and its a J1
He was told and i have since heard that you cant get the carbs correct with those
foam filters (Ramair's)and not to get too technical i think that opinion may be at least correct in some ways.
Steve Debben suggested that the best available reservoir of laminar flow is achieved with the OM air box.
This may or may not be so for slide carbs, i wouldnt know.
All i can say is that at full chocolates i have had the impression that the vacuum slides are oscillating up and down and giving a surging rather than linear power delivery. This after fitting a support bracket.
On the subject of jetting; ironically.... the last time i rode it, it was a f&*^%$g animal. It scared the cr^p out of me!
Mixture was a little weak of perfect mixture strength (point at which maximum horsepower is developed) and is currently running 130 mains and needle position is No.5 (clip at bottom of needle (richest setting))
This is standard 998 with standard cams, and premium unleaded. Timing is 2 degrees retarded from factory and its complicated but i wont mention the stage 3 dynajet kit because it's not actually there!!!!
All in all i would say that its too much darn trouble messing around for me and i wish to god someone hadnt buggered around with mine in the past. But it is what it is and i have been following a long slow path back to somewhere near standard.
That said i have just had it bored to 1170

and fitted a bigger valve head and higher lift cams so who am i to talk.
Oh and it should now have brakes for the first time since iv'e owned it!!
I shall follow my own advice and let the dyno boys set the mixture and jets when it's run in.
Hope this is of some use.
AL