Most new car nowadays use 4-2-1 extractors already out of factory. Take note of that. If you just want to change to some 4-2-1 you saw at accessories or exhaust workshops, you're just wasting money because they're made to replicate original extractor for replacement use only.

I believe a lot of people overlooked this.

If want to get performance gain by changing the extractor, get the one made by performance tuner, not some generic cap ayam.

swirling bullet is purely gimmick. the best way is not having bullet at all. or at least get a bullet with the smoothest inlet.

I would like to stress over and over again. Bullet does not add power. Show me a dyno chart to prove that bullet adds horsepower or torque.