Hi.
yes the c is a californian spec so its pretty much the cleanest model of it type at that time (emission saving design in 85...).
as nick says really.
anyway the general rule is if its close to the pass grade from std then just simply a tweak to the carbs/injecting, air box/filter and exhaust will be enough if it doesn't bugger up the rideability too much. there are things you could try to add (cannisters and extra baffles etc) but that depends on if that can be added or works with the old timer...the further away you are as std or modified to the pass the harder it is to get it to pass.
mine is a bandit 650s k5 2005 carb is still in the pass mark as bog standard for now, no doubt as the years tick on the pass mark will get a hellofalot higher and tighter no matter which arseho they sit behind that desk,so ill either have to tweak it or change it, so if advice was going id say newer it is the better long term.