Originally Posted by Tornado230
The EGR is as it says, exhaust gas re-circulation. I believe the purpose of the valve is to reduce combustion temperature to lower the NOx.
The main thing this does is reduce performance, as you are introducing an inert gas into the combustion chamber.
Having an EGR will not reduce performance, the EGR valve is only open at part throttle high vaccum, it is closed at high throttle openings, it also does not decrease milage, IF and only IF the carb is setup to take advantage ot the EGR (leaner jets than a non-egr setuup) and the ignition advance also is setup to add more advance when the EGR is open.
In general EGR does not effect either idle or high throttle operation, it is only open at low throttle settings and high manifold vacumm i.e. cruse condtions, where it does lower PEAK combustion temps to reduce the formation on NOx.
So it all come down to a tuning issue, if done right the EGR will not have any noticable effect vs. a non-EGR setup, the biggest problem is to get it all setup right, without spending huge amounts of time.