I had the JDL catted UEL header. Didn't add much power. As mentioned by @
churchx - a catted header provides minimal gains.
I had my header paired with a stock FP/OP and a Perrin 2.5" resonated catback. Sounded quite nice. Added some UEL rumble, and less additional volume than expected. Also seemed to cut some of the bass frequencies of the catback.
I ended up blowing up the cat and JDL replaced the header under warranty. I chose to sell it rather than reinstall, because I was trading in my '13. Note that they no longer warranty the cat.
TL;DR - Catless header or don't bother, unless you just want that UEL sound.