[adamant]

The stage 3 and QS are both claimed to neither add nor detract from stock hp.
If you want to compare the 2, I am sure there will be (if there isn't already), comparisons between stock/stage3 and stock/QS.
As for airflow, I read this before but it make's no sense to me. There is a significant amount of air exiting the exhaust that need to be taken into account. This additional air will reduce the lower pressure that the diffuser is trying to accomplish. So I would suggest that the further away from the diffuser the better the downforce. So the QS would be a better choice.
BTW I have the QS and I dyno'ed before and after installation. The difference between stock power and QS from the dynojet runs is not significant. But if pushed I would say that the QS generates slightly more power overall.
When I get some time I'll post the 2 best runs before and after the install.

 

[offroadr35]

do you honestly think you will ever be able to tell the difference in grip between a car with the Stage II and a car with the QS??

i really don't understand why there is even an issue with these two exhausts. The QS is built better, lighter, cheaper, and has been proven to make power.

 

[008]

do you honestly think you will ever be able to tell the difference in grip between a car with the Stage II and a car with the QS??

i really don't understand why there is even an issue with these two exhausts. The QS is built better, lighter, cheaper, and has been proven to make power.

First of all, why not take advantage of all aspects, why bother having a diffuser at all? There's people raving about the 10 pound weight savings. Do you think you'll feel it? But as part of the whole of weight savings it can be significant.

On the second part, 1. I can not speak to the build quality as I have'nt see the QS, but from the Satge 2s I've seen on the car and off, I don't feel quality will be an issue, 2. the Stage 2 is cheaper not the QS, 3. "has been proven to make power." hence the question I posted.

I am glad you like your purchase, I'm just evaluating the two. I'll mark you down for the QS side then.

 

[Stan]

Bear in mind that the present QS exhaust has been black flagged for noise at SCCA events. They have a quieter version coming out soon. Obviously that one has not yet been dynoed.

 

[Surferjer]

Notes about the exhausts:

The Stage 2 is only cheaper is you can do it yourself, and then only a few $. Are you comfortable cutting the diffuser? I'm not, but many are certainly capable of doing it.

The QS is lighter, might be a tad louder than Stage 2, and definitely makes more power than stock. I'd like to see Stage 2 dyno'd; I don't think I've seen a comparison against the other options. Both sound great.

Stage two seems to be having a weld issue with a bracket, too. The QS is still pretty new and could also have some quality problems, although none have shown up yet.

Since the noise issue came up, let's also point out that cutting the diffuser for the Stage 2 technically takes your car out of stock class for SCCA purposes.

Stage 2 tips point down, QS point out. Pick your preference. I picked QS because it was lighter and i thought I could put it on myself, which I did.

 

[BrianK]

Since the noise issue came up, let's also point out that cutting the diffuser for the Stage 2 technically takes your car out of stock class for SCCA purposes.

Does it make a difference if the cutting instructions are in the factory service manual?

 

[Surferjer]

My understanding is it does not make a difference, its still a violation. I'm not defending the rules, but that is what has been reported here by those who know a lot more than me. I think its dumb. This "violation" will likely never come into play at anything short of a the National Championships. Similarly, the noise factor won't around these parts (PA, NJ, MD).

Stan did say that he thought it possible to NOT cut the diffuser with Stage 2. I don't know, but the only way to find out is have someone with an uncut diffuser try to put it on a car with Stage 2. Next time I see Stan we can try it!

I want to mention the tone if different between Stage 2 and QS, too. Stage 2 is richer IMHO. QS seems to be more ragged or "throaty". Listen to them before purchasing!