Xforce
I love the sound my Elantra GT N line makes now. Can't talk about the gains as I also got a few other upgrades at the same time. I paid for installation about $200 as I had no way of getting under my car. The parts look pretty high quality and it came with all you need to install, I even got a bunch back after installation.
Sounds are worth it! 10/10
The quality seems pretty good I haven't even installed it yet I'm debating on installing or selling it just due to I can't find any shops that are willing to put it on and putting it on myself as a pain.
There's absolutely no instructions, so make sure you lay out your old mid pipe next to the new system. You will get a lot more pieces than you need. I think this is so if you wanted to up upgrade to the Xforce down pipe or muffler later on, you will have the hardware to do so. I thought the sound was going to be a lot louder than it was, but it is a pleasant improvement over the stock sound. Many people feel like these cars should have had louder exhaust from the factor, and this is as probably as close as you're going to get to that stocks feel and sound without screaming down the road. I did not use muffler cement, but do have some if a leak develops. It's been a few weeks and I have not noticed any leaks.
Gives the car extra power on acceleration.. and sounds good.. not whiney and not too loud with OEM muffler