Hi,
More of a 289 Guy, love the I-6’s, however. I’ll target this general old school. If burning your eyeballs out at idle & it was a Holley, I’d say power Valve, takes one ‘pop’ & it’s done for...but consider/test for these:
Caution: I’ve lost my eyebrows (need a GIF for this on SN, Wile E. Coyote?) more than once over a Carb/Carb(s), err..Pic above is pretty appropriate. Use care when observing inside Carb, throttling while running....
1)Moisture under the Dizzy Cap, take a peek that all is clean & otherwise well.
2)Running on all 6 Cylinders. Spare wires kicking around?
3) Choke sticking, hanging up, pulled in under acceleration..
4) Accelerator pump issue, leaking out around the squirter instead of through it.
5) Is fuel leaking internally through the overflow tube & being burned?, stuck Carb Float.
6) What is your Fuel Pressure at the Carb?(5-7lbs).
7) Vacuum Advance line crack, diaphragm rupture, or mech advance issue in Dizzy.
8) Coil (+/-) connections, Check all wires are seated well in the Cap, run in dark conditions to see Coil secondary arc’s between wires & Cap, wire to wire, may be able to hear it if Exhaust is quiet, etc.
9)May be a clogged line from Tank, limiting fuel sporadically to your mechanical pump. Quick Dx is Carefully pull the tank line off the pump, stick a 3/8” line on the Pump into a 5 Gallon gas can & see how she runs...Damp rag around where it enters the can to keep fumes down.
Good luck!
-John