I am still getting two codes that have me thinking if my MAF might be bad?
16806/P0422/001058 - Main Catalyst: Bank 1: Efficiency Below Threshold
and
16816/P0432 - Main Catalyst: Bank 2: Efficiency Below Threshold
what do you guys think this could be?

i was also getting 16537 oxygen sensor b2 s1 response too slow but replacing the sensor solved the issue.

17535 fuel trim bank 1 too rich and 17537 fuel trim bank 2 too rich also popped up before but ever since they were cleared they never came back.

this is on a 1999 a6 2.8q

 

if the code is gone after clearing them i wouldnt worry about it. maybe some oil dripped on them clogging them for a while and after some driving were cleared open. if it comes back then youll need new cats.

 

here is the thing about the cats, when i bought the car a few months ago the previous owner said that the car had 2 new cats and even gave me the receipt for the work. also when i looked under the car I did notice that the two new cats were a lot cleaner than the rest of the exhaust. i am pretty sure that the cats are universal ones so could this be the problem?

 

Aftermarket cats are crap!

I would make sure your fuel trim readings are good , replace any o/2 sensors that are old (not universal o/2's) , reset fault codes.

Are you using Vag-Com? If so you can verify repairs by setting readiness when finished!

 

I have the free version of vag-com using an ebay cable. I still don't know how to fully use it, can you explain to me how to do what you just said? lol

 

Go into 01 engines > measuring block 08 > group 032 > go & look at fuel trim values. They should all be about 0. You don't want to see more than 3 in either direction.
Remember if there is a - sign then the ecm is trying to remove fuel (too rich) & vice versa.