Bad fuel system/air intake

The code that referred to the maf sensor just refers to the maf circuit, it doesn't always mean it's the sensor itself, it could be a loose wire, etc. Did that code go away or is it still there or did it come back?
Was this a P0101, P0102 or P0103?

Well, the P0101 is a MAF sensor performance code, the P0300 is a random or multiple misfire code which could be caused by the MAF. The P0171 is a fuel trim system lean code which again could be caused by the MAF and/or a vacuum leak. A vacuum leak after the MAF could also cause a P0171 as well as the P0110, too. So check all the clamps, etc around the MAF and the duct work for a leak and make sure all the clamps are tight.
The P0496 does have to do with the EVAP flow during non-purge. That refers to a undesirable intake manifold vacuum to the EVAP system. This again could be due to a vacuum leak. So again rule out any and all possibilities of vacuum leaks, go around make sure all clamps are tight and no leaks. Once you find and fix any leaks, all of them codes should go away.
If you cannot find any leaks, you may want to try replacing the purge solenoid valve and see how many codes go away if not all of them go away.

I do not think it is a catalytic converter issue. That would most likely have a code for it like a P0420 or even an O2 code. Checking for the leak first will not cost anything. Let me know if you do not find a leak. Rockauto has an AC/Delco purge valve for $20.00 just in case. https://www.rockauto.com/en/moreinfo.php?pk=926315&cc=1432073&jsn=446

Here is the test for the P0171, which is about the closest to a catalytic converter problem but as you see, one of the first tests if checking for an intake air leak. Also, the test for the P0101 also is checking for an air intake leak.