I know things... A lot of things.
Join Date: Feb 2015
Motorcycle: GSXR 750 K4
Re: 2nd air and what does it do?
It basically allows fresh air to enter the exhaust tract near the valve under certain conditions (e.g. only on overrun or when not under load). It allows the unburnt portions of the exhaust gases to burn more fully, lowering emissions. Since it has zero effect on performance while lessening your impact on the environment, there's no reason to remove it once the OEM took the trouble to design and install it, unless you're feeling particularly antisocial.