EGR valves are designed to recirculate some of the engines exhaust gasses back into the engine, as a result, a vehicle omits fewer emissions.
While this may be good news for the environment, this comes at an expense to the driver because of the limited serviceability of EGR valves. Exhaust gas recirculation causes carbon build up the within EGR itself, the inlet manifold, and engine Internals. This can eventually lead to clogging and mechanical breakdown.
Removal of the EGR system results in lowered engine temperatures, improved throttle response and economy and also can lengthen engine life by reducing oil contamination and carbon deposits.