After reading a bit on Roasty Ducks thread on resistance on plugs I checked one of mine. 3.5kOhm. When hot it drops to 2.5kOhm.

I looked at this vid and it says it should be 4k to 8k Ohm. Presume then my plugs are stuffed. Now I dont by any means mind getting new plugs but am interested if this is correct.

 

1: It depends on what plugs you run
2: NKG uses a 5k resistor
3: The resistor is for suppressing RFI
Testing resistance could tell you if there was an open, or ultra high resistance..but it does not address the condition of the center electrode ..is it eroded? is it coated by deposits?
And it could tell if there was a short between center electrode and metal body.
Both of those are good tests, hot and cold.... but not really a definitive test for condition and serviceability.

His suggestion to use a wire brush to clean deposits off the plug is way off base.. doing that will deposit metal on the insulator and or electrode and likely cause a misfire or outright failed plug.
It was common to use a "Spark plug cleaner" when I started out in the early 80's. Knowing what i know now about media blasting, I would never clean a plug like that....way too likely media will get trapped in the plug and release later while in use.

 

Im using NGK Irridiums.