Go for it ............... MY exhaust showed a 9 bhp improvement with no other mods [ note for PDG ]. Instead of sounding like a strangulated fart, the exhaust note took on a purposeful and not over loud note. As noted - the weight saving alone is worthwhile.
An actual quantifiable number? Are you feeling alright? :neener:
Anyway, because my job appears to be official nitpicker, I shall continue... 'An' increase isn't really a surprise, especially if it's at high revs - it's 'how' the increase happens that is important. Where in the rev range was the increase present? Did you lose out anywhere in the band? If you gained 9bhp above 7,250rpm, but lost 7bhp between 2 and 4k, then it would actually be less usable on the road imo.
If however you managed to, say, keep the p/t curve the same up to 6k, then had a peak power increase you did very well indeed and in that (or better) case I will very happily stand corrected.
As a general 'rule' (with exceptions and limitations), a free flowing large bore pipe will produce more top end power at the expense of low- and mid-range torque, while a seemingly 'more restrictive' small-bore system will perform better at lower speed while 'strangling' the engine as the speed increases. Most 'sports' exhausts claim (and usually deliver) power increases (on any engine - car, bike, tractor, etc.) but it's almost always at peak power - near or at the redline - fine if you intend to be running like that most of the time (for 'sports' for example) but around town?
As with any 'tuning', it's down to use and what you are prepared to live with. I rode a bike some time ago that had a nitrous shift system and lock-up clutch. The 1/4mile times were massively improved over stock and it was hugely entertaining, but for 'normal' road use it was almost unbearable. A highly strung, peaky, rev-happy engine is great fun to ride as a toy, but for everyday transport it very quickly becomes hard work.
