Maybe you're confusing MMO with something else:
(From their website) - (http://www.marvelmysteryoil.com/index.php/site/mmo/)
"Marvel should be added to your engine oil at every oil change. In a traditional automobile engine with a 5 quart oil capacity, simply replace one of the engine oil quarts with a quart of Marvel. For your convenience, MM13R is the quart size of Marvel Mystery Oil? and can be found at most automotive parts and supply retailers and mass merchants. Marvel is also safe and effective to use with synthetic and synthetic-blend motor oils."
Heck, you can buy it in anything from 16 oz to 55 gallon drums...
Anyways, it did seem to run better, but the next day it was back to the same old popping and hesitating that it has always been doing. I then took it to the dealer nearby, and they told me that no doubt about it, my ignition coils were bad (1,5,6). I bit the bullet and bought 6 new ones from Advance Auto Parts. As I was swapping them out, I checked the spark plugs that the last mechanic installed and they were all gapped wrong - they were all at .040-.042, as I understand it it should be .054. Fixed that, replaced all coils. Since then, I haven't heard a pop or had it miss or hesitate at all! So something must be working right again.
It still idles kinda rough, and after a trip of about 200 miles the CEL came on again - said misfire in cylinders 2 and 3. Grrr... The CEL went off again after a bit, and I haven't seen it since. Hoping to get it checked out more, but for the moment the worst seems to have been solved.