Exhaust Change...Main Jet Change?

So, I'm thinking of changing the exhaust on my 500T and was curious as to whether anybody could give me a little guidance on how much I'd have to change my main jets (if that's even the correct one to change) after the switch...here's a link for the eBay auction for the potentially new exhausts...
http://cgi.ebay.com/ebaymotors/ws/e...50002332725&rd=1&sspagename=STRK:MEWA:IT&rd=1

i think my stock mains are 150 (but i'm out of town and could be wrong) so, would i go for 147.5,145, 152.5,or 155?
gracias mis amigos.