I wouldn't condemn the MMO or blame it for carbon. First MILLIONS of cars, new and old drink the stuff mixed with gas, and have done so for 60+ years. If it did carbon foul engines, there would be tons of posts condemning it on all kinds of forums- Studes, Buicks, Chebbies, etc. Seems like the opposite is true- engines that run it seem to have cleaner chambers. MMO is not just straight oil, it is a mix that includes various benzols and aromatic esters, all known by petro engineers that blend gas for their ability to clean, not foul combustion chambers. 4 oz in your 10 gallons is a 320:1 ratio. Two cycles run oil at ten times that, 32:1, and don't carbon foul unless you run rich, retarded, cold, and slow-lugging. Those same things foul ANY infernal (and I do mean
infernal, not internal) combustion engine.
So, let's analyze this: You say the noise has increased since using MMO. Two factors come to mind:
1) Time. Whatever is making the noise may have progressed to a worsening, louder state even if you never used MMO. examples- Weak or fractured valve springs, warped cam/ too much bearing clearance, cam oscillating fore and aft due to that spring/plunger thingie in the gear cover, You may have a regrind cam that has any of many grinding errors on
one of the lobes. You may have a cracked ring. You may have a chip on the crank gear or timing gear. Try shorting plugs one by one at a fast idle and see if one particular cyl is associated. Get a $10 stethoscope and play doctor. Try a different dizzy. The dizzy drive gear may be the culprit. See if it goes away with the clutch depressed, loading thrust on the crank. It may be that Nu-Rex centrifugal advance that I sold you a year ago bouncing around or tapping on something.

Ask Ken Ehrenhofer or one of those Friday night garage boys to take a listen.
2) Things may have changed by the
cleaning and lubricating effect of MMO. You may have had valve stems that were a little sluggish in their action and now 'snap to' freely, making one with excessive lash noisier than before. MMO is known for freeing sticky valve guides.
If you open the chamber to check lash, change out the valve springs. An air line Milton fitting attached to an old plug base and 90psi will give you over 150 lbs closure on each 1.5" valve, making keeper removal easy.