When I modified the cans on my 800 monster I had the dealer raise the settings up +2 points, when I opened up the air box with a k&n filter we raised it another +5 points.
As long as it doesnt run lean (white coloured plugs) and pulls smoothly you should be ok.
If you do a lot of around town running your plugs will look a lot darker than if you just do mainly long rides.
Idealy a pc3 is the way to go if you do a lot of commuting.
Going through the same delema with the s4 I have just brought, trail and error.

Doon