can anyone explain to me exactly what the air pump is for? Im talking about the guy that has a very larg hose connecting to a device coming off the passenger side exhaust manifold and a very small hard line vacuum to the TBI

 

The thought is that by injecting fresh air into the exhaust system, it will increase catalytic converter efficiency and life. Older converters required it or else they would melt down rather fast. Newer converter element designs really do not need them though.

Depending on your local emissions laws, it may be illegal to defeat or remove said system.