[Alfanut]

The QS HH is a lovely thing. It does exactly as advertised. No drone. No headaches. No fatigue. It makes a two tone note that I think is richer than the flat note from the oem race….The note is actually a little higher than the race and not quite as loud. It turns the exhaust into a four into one system as little exhaust gas flows out the right hand exit. Since there are no sharp curves, just a nice flowing S-bend and uniform diameter tubing, exhaust gas speed doesn’t change much through its length so it’s an efficient system. No noticeable performance loss or gain on the road. I’ve had mine on my 4C for six years without any issue.
The only negative for some is the angle at which the exhaust tips exit the rear. I’m not THAT ocd about it. For me it’s a point of difference, not a negative. Simple and effective. Highly recommended by me.

 

[Alfanut]

Although this is not an issue in my area it is a very good point. Thanks.

It’s more of an issue if you run track type tyres on the road. My Pirellis are reasonably quiet (until they wear). My RS4 Hankooks sounded like I had worn wheel bearings they were so noisy. It’s the reason I ditched them for Cup2s.

 

[Alfanut]

If you want to hear your exhaust put on a set of Cup 2s. They’ve really surprised me with their quietness. It might be something to do with the lack of sipes and only 3 straight channels for air and rubber to vibrate. Whatever the reason, it’s considerably quieter in the cabin with these. That’ll probably change as the tyres wear but at present they are impressively quiet. I can now easily hear the raspiness of the QS on a steady throttle at 110km/h with the windows up.

 

[Alfanut]

Are saying all the drama is there when the flap is closed bypassing the Helmholtz resonator?

No flap. It’s the non-valved Helmholtz being discussed.