I really don't like EGR's on LT1 engines because they are mounted at the rear on the intake manifold and i appears to me that only the two rear cylinders are getting any oxygen free air. They would have to be running too lean and overheating causing head gasket failure. Also the PCM advances the timing when EGR is open and the forward cylinders would be close to a detonation damaging condition.

I guess my Question is " Does the intake manifold somehow port the EGR gas to the front ? Or is the gas staying in the rear area of the intake manifold ? "

 

In order for EGR to work it has to be distributed equally to all cylinders, so I am sure GM knows what they are doing in this respect. EGR does not make the engine run lean, all it does is to displace atmospheric air with inert gas, thereby reducing combustion temperature. The A/F mixture is controlled by the O2 sensors by reacting to the amount of oxygen left in the exhaust. Detonation in these engines is controlled by the KS sensor, and the PCM knows which cylinder is detonating and can adjust ignition timing individually for each cylinder. Also at WOT when the engine is under stress, the EGR is closed and the engine A/F ratio and timing is controlled by pre set maps in the PCM memory.
An good side effect of EGR is that by reducing combustion temp at part throttle, is that more spark advence is tolerated resulting in better fuel economy.