I have an intermittent rough idle issue in a KJ2.

I've been looking at the service record of the car and noticed this when this was checked at Mitsubishi:
Check for runs rough in drive at idle
Clean throttle body reset base idle
Requires new engine mount bracket <---- Does this mean the engine mount itself or is this something different?
Center muffler damaged (still serviceable) <---- This is the resonator? How can they say it's damaged?
Engine pipe damaged (still serviceable) <---- What is this in reference to?

The rough idle isn't always there. Sometimes it's fine, other times it's pretty bad. Usually the longer it runs the worse the idle gets. After a long trip it idles bad even in N or P, seems like it's missing or something.
Otherwise engine is silky smooth throughout the revrange.

Any recommendations?

I recommend you go out to the car and look at the engine mount bracket and exhaust system to see what that is all about.

Center muffler damaged (still serviceable) <---- This is the resonator? How can they say it's damaged?
Engine pipe damaged (still serviceable) <---- What is this in reference to?

Sounds like the car has driven over something and caught the front resonator and also damaged the engine pipe that feeds into it. You will find dents in it i bet.
If these are all noted at the same time and the mount this may point to a big shunt to the exhaust which was enough to move/jolt the motor and damage the mount......... Needs a carefull look and check no other damage not reported. Vee

Thanks will have a look.
Though the car has been on a hoist twice now and the mechanic made no mention of anything down there.
The report is from 65,000km ago and the mounts all seem in good condition to me

So this is old news and nothing has broken or fallen off since then? You have nothing to worry about in that case.

As it says "Still serviceable" and there is no record of repair I am not sure if it's still a problem?