I have researched, and I'll continue to disagree that there is any performance, driveability or milage benefit to EGR. The
sole reason for EGR is to reduce unburned hydrocarbons - in older engines this was done to meet emissions standards, in newer ones it's done to prolong the life of catalytic converters. All this is "useful" in terms of meeting emissions standards (A Good Thing), but demonstrates no
performance benefit. From a thermodynamics perspective (I hope we don't go there
the overall efficiency of the engine is higher because the unburned fuel in the exhaust gets a "second chance" and so more is burned...
EGR dilutes and heats the intake charge - which results in lower peak combustion temperatures (as the charge is less dense) but also less specific power.
More cam overlap actually makes the problem
worse, as more unburned fuel escapes through the exhaust valve. The purpose of overlap is to allow higher volumetric efficiency - the escaping exhaust gases pull the intake charge in - but significant overlap means significant intake charge escapes at lower RPM.
Good discussion, many viewpoints