does anyone out there know anything about them. hp gains, sound, build quality etc. ?

 

I have the Milltek stainless steel header and hi-flow cat running into the Magnaflow cat back exhaust on my MCS. I haven't noticed any increase in volume but the exhaust pitch is somewhat higher.
The build quality seems pretty good. Nice welds, smooth tubing bends. Purchased mine from Mini Sport in the UK. Around $870 including shipping based on the exchange rate in May.

 

Any idea on horsepower gains from this set up? I have the Magnaflow exhaust and am looking to add the header. How much difference does the header contribute?