Dry carbon fouled plugs means rich mixture. "Tuning" the carbs means different things to different folks. Carb synch is not carb tuning.
The D8EA plugs are correct if you have resistor plug caps. D8ES plugs have been discontinued, they were designed to work over a wider heat range than the D8EA but were banned by the EPA for some reason.
There are a variety of plugs that will fit but that's not your problem. If the bike seems to be running OK the ignition at 10V is OK, but cleaning all the bullet connectors in the wiring harness is a good plan and that can reduce voltage loss to the coils. If you feel missing at higher throttle, the spark might be weak and the extra fuel from a "missed" ignition can foul a plug when it does fire.
Check float levels. This is something many mechanics unused to our old carbs get wrong.
Make sure the chokes are coming all the way open. I've had exactly what you describe happen after leaving the choke on, a maladjusted mechanism can leave the plates partially closed with the lever all the way down.
Replacing ANY jets on a 2446 mile stock bike is just plain nuts. The Keihin original jets would be indistinguishable from factory new at that mileage. Most if not all aftermarket (ie Keyster) jets should be used only for retuning with a overbore/header/cam/pods or whatever - the numbers seem the same but a 85 Keihin is not identical to a 85 Keyster. Just going back to the OEM jets and needles would likely sort you out if someone installed aftermarket brass.
A clogged air filter or anything blocking the airbox snorkel will cause a rich mixture by choking the intakes. I have seen some aftermarket filters with very poor filter material, way too thick and restrictive. Try the bike with no filter and see what happens. This is OK for a test ride, stay away from dirt roads or super dusty situations though.
