Here's the deal in plain English:
I dyno the exhaust. It makes 430hp.
You dyno the exhaust. It makes 440hp. Our dynos are different, on different days, with different people running them, under different conditions.
If I post dyno numbers, I have to stick to them, even though that's not possible. If I say the exhaust makes 430hp, and it makes 440hp on your dyno because of your setup, your dyno, or your conditions, I'm in trouble. The lack of consistency inherent in dyno testing means that I stay away from quoting numbers you may or may not get.
You can test backpressure- a figure directly related to the amount of air the exhaust flows at a given RPM, and get an easily repeatable figure than you can verify. This is more compatible with the scientific method, and I am therefore more comfortable quoting this figure.
This is the exact reason that nearly nobody in the industry dynos their systems.
In any case, we've got a dyno day scheduled at Fall-Line Motorsports in Chicago when the M3 comes back from it's photoshoot in California. We've had this scheduled for some time now, and are only waiting on Fall Line's racing schedule, and our own travel schedule to coincide so that we can do some testing of the exhaust, as well as a number of other parts, on their dyno. Even at that point, I'm NOT going to use dyno graphs to sell the exhaust, as it's NOT something you can take home with you.
You can be guaranteed that when you put the exhaust on your car, it will sound just as fantastic as ours. You can be guaranteed that the system is handmade, in Germany, from excellent quality stainless steel. All of these things, I can stand behind. I CANNOT guarantee that you will get the same dyno numbers as I do, when you put your car on YOUR dyno. I can't control your environment, your engine's condition, or your dyno operator's level of competency.
I think I've explained my stance enough. I can only guarantee things that are in my control, that's what it comes down to.
I'm going to stop here.