I have not been using a bsd system for a long long time, but from what I recall at least freebsd had the same kind of virtual FSs that linux had, procfs on /proc and devfs on /dev but no separate sysfs on /sys.

I suspect though that you may have wanted to investigate sysctl(8) for your tweaking needs http://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=...