I was surprised at how nice this exhaust sounded. I own a WRX STI and am used to that "Subaru Rumble" that Unequal Length Headers provide. The stock WRX has Equal Length headers so most of the exhaust systems I had heard up to this point had sounded fairly generic and had lost their character. While certainly not as obvious, the Gemini R400 manages to bring a light warble to the sound, especially at lower RPMs. The pops and bangs accompanying each lift and shift are fun, too.
Like most Invidia products, the fitment and finish is great. The exhaust outlets are a little wider than I expected based on the pictures I had seen before. They fill out nearly every inch of space provided by the stock WRX bumper and have that crisp engraving on the side. Things bolt up where they should be and the whole install was a piece of cake.
Perhaps the most satisfying thing about the R400 is that you can enjoy a lively exhaust without obnoxious cabin noise or drone. It's relatively calm under normal city driving but playful and enjoyable with a quick dab of throttle. Even when under hard acceleration, with the windows up, you can easily talk to the person next to you as you row through the gears. Downshifting to a stop some drone manages to make it's way through, but it's not noticeable enough to be a deal breaker.
There's a reason the Gemini R400 was tough to come by when they first came out. Response was far higher than Invidia expected and the recall on the first batch backed up things even more. My friend waited two months to get this exhaust system but, after testing and tuning his WRX, we both agree it was worth the wait. This system works great on the WRX and WRX STI, but I feel like there's a shortage of exhaust systems that I like on the WRX while there's a good long list to choose from with the WRX STI. For that reason, the Gemini stands out to me as an excellent choice for 2015+ WRX owners looking for a solid upgrade.