Mondial QV Misfire

My 1983 Mondial QV just developed an off idle misfire under load. It seems to idle fine, but when you take off in first gear it will stumble and misfire until it reaches higher revs. Seems when it's misfiring that revving the engine helps it clear its throat, but then at the next stop it happens again when taking off. It drives fine once underway, just seems to be a low rpm under load issue.

I had the identical problem last year and found a couple of spark plug wire extenders had holes burnt in them, replaced all 8 and misfire was fixed. This was the first thing I checked since the symptoms appear to be exactly the same, but all extenders appear to be in good condition and they're less than a year old with only a few hundred miles since installation. The spark plugs are also new, and other recent repairs include a rebuilt alternator and new battery.

Any suggestions of where to look next? In my head it seems it should be a plug extender and I'm tempted to pull them again and try and check resistance.

 

Thanks, the plug wires came on the car when I bought it, records show they are several years old. I'll check plug wire resistance and see if I can identify a bad one before ordering a new set. Same on the coils, will check those as well. I'm sure it's an ignition system issue, just too similar of symptoms to when the plug extenders were shorting out.