Ok. I have had my 2006 gs500f now for awhile. I want to up grade and modify. i've been reading the messages they have helped alot. so far the upgrades I have are

zero gravity double bubble windscreen
changed out the stock front pegs with gsx-r rear pegs
changed the seatskin out with matching paint schem (navy blue and white) (second-look.com)
stage one jet kit
jardin rt1 can

My question is
i want to change my stock 16t front sprocket with a 14t sprocket.
will i need to get a new chain?
if so what size?
and where can i purchase?

next questions,
what is a lunch box?
where can i get one
and does it breath better than a k&n drop in?

please help a lost soul. //

If your chain is still fairly new, you may be able to get by for a while just backing the adjusters out a lot.  I would suggest just getting a new chain in the right size though.

A 'lunchbox' is K&N part no. RU-2970.  Most auto parts stores can order it for you at a cost of about $40.  Yes it will breath a lot more than a drop in though carb rejetting is required for either.

I'm still shamelessly promoting this link, and no I have no affiliation with Amazon, it's just the best price I've found and shipping is free.

http://www.amazon.com/gp/product/B00062YQXE

I got one on amazon, but I also got a drop-in.  I paid 35 for the drop in and ran it all of 500 miles before doing a bunch more work.  I'll sell you that for next to nothing if you want to try it.

got a picture iof your bike, I was looking at seconlook.com seats and their pics are crap...
very curious about those.  common man post up your pick

as for airbox, if you go beyond the drop in k&N filter you will need to rejet your bike... keep that in mind. so if your going to do that, might as well to go all out and get airbox changed over, and get exhaust done as well., then reject it ortherwize you will be rejectting twice.