Question on reducing Munin resource consumption
To disable plugins, on every node (not just the master) remove the plugin symlinks you don't want from the plugins directory (usually /etc/munin/plugins/) and restart munin-node (e.g. /etc/init.d/munin-node restart). If you've put any custom plugins in that directory that aren't symlinks, remember to move them somewhere safe instead of deleting them in case you want them later.
The master should pick up the changes on the next run.
Edit: if you don't want to delete anything from /etc/munin/plugins, you can add an
Edit 2: if the issue is only resource consumption on the master, Munin 2.0 has a number of features that help reduce it: you can cut the amount of I/O using rrdcached, and you can cut the amount of CPU used by generating HTML and graphs on demand. Both come at the cost of slightly increased memory consumption.