We rejet to correct the epa mandated lean run carb.
This by itself can cause the backfire issue so many complain of.
It will also cause the header to turn gold then blue due to overheating.
1st pull your sparkplug and compare
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1222357450/1#1next remove the brass plug and adjust your idle mixture
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1221818822This usually fixes most people but you've also changed you exhaust and that may affect the adjustment of the main jet. I've got a simple test for that. Find yourself a good long grade, one that you can go up WOT (wide open throttle) and get a steady speed with at wot. Now back off the throttle alittle bit, does it seem to pick up a little? If it does, you need the next size up.
The white spacer or needle spacer mod is little more difficult to determine need. At least I think so cause I don't need. Problems like surging while cruising along or lack of get up and go may be a reason to mess with it.
You want to tackle these mods one at a time. Get a good feel for whats wrong then you know what you're looking for. and read the carb tuning posts and how-to's while you're waiting.