Electrical gremlins
 

Not sure if these are related, but 2 problems I'm having.
The first is terrible static using AM radio. It is rpm sensitive. Mostly with the choke on, but I thought that was completely manual. It has new plugs, wires, cap, rotor, battery cables. All grounds have been cleaned. It only happens between 3 and 5 Rpms.

The second issue is a slight stumble when cold. Do spark plugs make a big difference? All I could find local were motor craft, but might order better ones if people think they could be the issue.
I have an 85 GS with 55k miles, everything else is original. Thanks in advance.

Use NGK plugs.They may help.

As to the radio, you could see if there are any capicators bolted to the body at some points under the hood. They should be shown on a wiring diagram, if you have one. I've always thought that those things were for noise suppression but not entirely sure. I've seen one near the ign coil on some cars. Not sure if FBs have any.

Thanks, ordered the new plugs. There are 2 capacitors one on the dizzy and one under the rats nest. Ordered those too. The only issue left is a dragging starter, which I will tackle this weekend.

hmm.. radio issue is interesting, i have a golf 1.8T and is also sensitive to RPM.. im interested to see if your new caps solve the problem!

It's usually caused by voltage fluctuation, so the capacitors should help it. They are usually labelled as radio noise suppression capacitors. I would also check to see if the plug wires are causing noise. If they are resting on/near a power wire, they can cause RPM sensitive noise.

Ok, got all my parts, 2 capacitor things and factory plugs, so I'll report back tomorrow after I install.

Put the capacitors in and they immediately fixed the static. Then on to the plugs where they really made a big difference on both cold and warm start. I also noticed an improvement in overall drivability. Thanks for the suggestions.

Bravo! Thanks for the update.