I have some probable cause that my stock cat is headed towards being used up (periodic rotten eggs smell) @ 116.5k miles. I have a gently used high flow that I can swap it out with, but I don't know if its going to throw a flag on my next inspection? The rest of the exhaust is stock.

 

The high flow will pass, as it is still a catalyst. If you lived in Northern VA it would be a different issue since they have emissions testing, but areas south of Fredericksburg don't have to deal with emissions testing yet.

 

The other thing I'm looking at is mating this 3" cat with the stock parts, if that will work or will there be problems?