As part of trying to diagnose a rough idle I had a look at the distributor cap and rotor condition.

It looked fine to me as there didn't seem to be any particular wear that has taken metal out.
The tabs seems in tact, though had some white stuff around them.
The rotor seemed to have a bit more wear and it felt like sandpaper to the touch.

Can someone tell me of this is ok or needs replacing?

EDIT:
At 196,000km, does this look like it was renewed at some stage?

EDIT 2:
I read that some distributors have a vacuum sensor of types and change the timing slightly. Often when this doesn't work it causes rough idle.
Can anyone confirm/deny if the 3rd gen distributor changes timing at all?

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Get a bit of sand paper and clean the white stuff off, it's not hard.

Don't clean it. Your only removing material making the spark jump further. It's hard to tell as your pics are slightly out of focus, the rotor looks like the spark is originating away from the edge. If it runs well under load chances are it is ok. Vacuum advance was on old carbi engines. AFAIK the ECU controls all ignition timing advance.

Jimbo, what does this mean if the spark is originating away from the edge?

It runs well under load, but the idle is choppy

But the ECU can't control the spark if the spark is weak because the dizzy cap looks like that!

What would you prefer to do spend a few dollars clean it up and if that doesn't work buy a new dizzy cap and rotor or just go and spend up on the cap and rotor.

Does it look like it is in poor condition?
I can't tell as I haven't a clue but it seems fine to me seeing as the tabs on the cap are full and just have some residue/powder over them.
The rotor I don't know, it seems to have more wear on it than the cap but again don't know if that causes an issue?

Bits look original but serviceable. Check that the centre pin of the cap is still spring loaded.
Clean the inside with a dry paint brush, just to move the dust.
The outside of the distributor cap looks dirty or oily - leaking?

There is no vacuum control on the distributor, nor is ignition timing adjustable on the distributor - base timing and advance are all part of control by the ECU.

Yeah there is an oil leak coming out from the bottom. Time to replace the o-rings but not sure if it's a good idea to replace the distributor, cap and rotor while at it to try and get rid of the choppy idle?

Jimbo, what does this mean if the spark is originating away from the edge?

It runs well under load, but the idle is choppy

The spark has further to travel which coud reduce its strength.

The spark has further to travel which coud reduce its strength.

Considering the high tension side of the ignition system can throw a spark in air of about 2 cm, I don't think this is going to be much of a problem.

Spetz: I would fix the oil leak and have a good clean up in that area, and then see how it runs.

I dont mean to make you out to be a dumb arse mate, you know your car better than anyone else...but

Are you certain that this issue isnt just the normal rough idle that most of the 6g74/5 engines suffer from?, some cars are worse than others, just asking as id hate to see you chase your taik over something youll never fix

Perhaps post a youtube video of your engine running so we can listen to it?

What happens when you lift revs to say around 2000rpm?

Remove the dist, put a new seal in, get a new cap and rotor (we have Bosch ones far cheaper than the dealers sell genuine ones for) and replace them both. This may not be the issue but cleaning is NOT an option, while I have seen worse there is still quite a bit of wear on these items and if I was doing a diagnosis I would replace them, no use chasing your ass when you know in the back of your mind there may be an issue there

Also, if plug leads are original (will have year printed on them) may be also worthwhile while you are at is as often the ends of the leads will break off inside the cap, again with leads we only use genuine (lets face it, the original set got the car over 200k over 12 years so a new set will do the same)

Ricbec, at times the car idles acceptable (never smooth, but at it's best it's good enough to not warrant looking into).
The issue is that every now and then it starts idling really poorly, similar to what I would expect if a cylinder was not firing at all.
I am aware these are not the best idling cars, and I have been in some that idled really well and some that idle essentially identical to mine. I don't know if this issue can be solved but I certainly feel something isn't right.

Madmagna, do you think I need to change the distributor or just the cap/rotor?
The car runs fine other than idle, except a bit of harshness from the engine around 1,500-1,800rpm under load. Though nothing which is very pronounced.