After a week or two of using the kiehan headers + Akropovic can this is what I've found.
Can't say the noise of the bike has increased by much at all by changing the exhaust. Fruitier yes but not much if at all louder unless the baffles are removed.
The headers golden in a single ride and if left (after a few rides) will take a bit of time to polish back to shiny silver headers using brillow pad and autosolve.
The headers look very similar to the original less the cat and overall weight with Akropovic is better and lighter.
Performance is briskier and it pulls better through the rev range than before. Although I must add that since changing my exhausts I've been meaning to get BMW to look at my bike cause there are a couple of flat spots I didn't have before which is annoying now!
Having spent £760 changing the exhaust system do I regret it?? NO. Is it worth the money?? Hard to say, it is expensive for what you get out of it but I'm glad I could afford to do it put it that way!
