But what does it do????? Why do we want to re-circulate exhaust gasses?
Simple. The EGR system's primary purpose is to keep combustion temperatures down. Why? Because if the combustion temperature reaches a certain point, NOX is formed, or Oxides of Nitrogen. This gas, when it exits your car, moves up into the atmosphere. When exposed to sunlight, it helps crate smog. By re-circulating inert exhaust gas we "fill-up" some of the cylinder. By doing this we decrease the combustion temperature.
Some side effects of removing the EGR system.
Not sure on an EFI setup.
Carb setup, the increased temperatures can cause some carbon deposits in the cylinder to remain hot enough after you shut the key off to keep igniting the fuel being drawn into the cylinder as the motor is coming to a stop. result, dieseling, big time. I have this problem. I have found that running 91 octane fuel virtually eliminates this problem.