What are the best headers and test pipes? What will give me more hp/tq? I think the long tube headers are too loud for me. I got Stillen Gen 3 Intake and FI Exhaust and I want to get an uprev tune when everything is in place. Sorry if I'm in the wrong section.

 

You'll gain more power out of LTHs more than shorties, we can recommend you some brands out there if you settled on these.
As for Testpipes, Art pipes are the way to go .. more gain (dyno proven) , less scream than any other TPs out there.

 

I had FI double resonated TPs and loved them with my FI exhaust.

 

What about High Flow Cats? which gives more hp/tq and keeps the low deep sound? with little rasp.

 

TPs are going to. They give you better flow.

 

If I remember right the WHP diff is like 2-3 , not worth it an not be be emmisons legal. I have a couple vids posted in FI RHFC'S thread . The sound is amazing . Nice and Deep !