I am getting my TDX2 + Art pipes settup soon, could I still upgrade HFCs?
If so, what are good HFCs that I should buy?

Also are headers worth it?

 

The ART pipes replace the cats/HFC's so you can't use them in conjunction with one another. Headers don't do much for performance but they amplify the exhaust nicely. If money is a concern then don't bother with headers.

 

Thanks alot! Thats the exact answer I was looking for.