Originally Posted by Toink
BTW what difference did you notice with the K&N air intake? Did you install it directly with the sec. cat replacement or did you do them one by one. Which difference did you notice from the one and the other?
I'm thinking of similar mods to my '10 Z4 35is which is now still stock, to make it sound a bit more. In the future I'll get custom software on it.
I only have the K&N filter, not the whole box. No difference in power or sound
When I did the second cat deletion it was difference in sound and power. It felt like it was faster on high revs and the sound was more of a scream when you got to those high revs. Some popping in the exhaust when I go off throttle is also a difference to stock.
SKN Tuning have done a dyno test with the Milltek exhaust and it gave 13bhp and 19nm of torque extra on stock engine. They say that the cat deletion does the most of the power. I do also have the ESS Stage two, that give more power from the Milltek straight pipes.