jetting after exhaust installation

hi, i have slip on exhausts on my '76 kz400d. i hacked off the original silencers b/c they were rotten. do i need to re-jet the carbs? and if so, do i go leaner or richer? more/less back pressure = rich/lean? how does that work?

pk

I would look inside the mufflers & compare them if possible.
Check to see if they appear to be about the same.
If the new ones seem to be less baffled, then there would be less back pressure, so they might flow more air which would make the bike run more lean.

If they are way louder than stock, you may need richer jets. If it runs good and the plugs are the right color, no worries.