Air box mod save $$$

[flynrider]

If the bike sounds louder or different the rider will tend to think there is a performance gain. Some of this is probably an unconscious desire to justify the work done or money spent, on the mod. Just human nature so something to be mindful of (and dyno does not care one way or the other)

No way to really tell until you dyno it. Nothing like cold hard facts.

That is so true. I used to operate the dyno at my friend's bike shop on the weekends (back in the 80s). There were a lot of folks that were certain they'd bumped up the hp by just slapping a pipe on their UJM and making no other changes . While their bikes were certainly much louder, invariably the dyno showed they had less power than before. Even after the proper tuning of intake and exhaust mods were done, the extra power usually showed up at rpms that the rider rarely saw on the street.

The shop had a race bike that we constantly tuned and retuned using both the dyno and a set of test pipes equipped with fast response EGT probes (fancy stuff back then!). Even with all that equipment it was often difficult to get the right combination of mods tweaked just right to produce more power.

Things are a bit easier these days with an ECM in charge, but even so, performance tuning is still a bit more art than science.