I just purchased a used 02 passat wagon with complete care records, total miles: 189700. I put 85 octane in it, about 3/4 tank, and it ran fine for about 2 days. Yesterday, my MIL light came on and then starting flashing after a while. The light is always on, and flashes occasionally, especially upon acceleration. The car chugs and at times idels rough. (at about 3 gallons left in the tank of 85, I filled it with 91, and added octance booster). I ran it for 50 miles and still having symptoms. AutoZone ran the codes and they are P0301:cyl 1 misfire and 90420:catalyst system efficiency below threshold, bank 1. Do you really think it is my cat.convert.? Is the misfire enough to be drowning my catconvert? I have obviously been reading forums and such! 
I put 85 in my turbo VW for crying out loud.
I’m willing to bet you have a bad ignition coil.
switch the coils between cyls 1 and 2, clear the codes and see what new codes appear (back at autozone). If the new code is for cyl #2 misfire, then you know that coil is the culprit. They’re inexpensive if you search around online.
Thank you so much for the reply, that’s a good way to trouble shoot. I appreciate your time.