For someone who claims to know something that is as good as saying you don't. I didn't say chrysler used the same engines for all those years I said the EGR's were all pretty much the same in that era. The means of controlling the vacuum, which determined how much exhaust gas was delivered and when it was delivered is what changed depending on make, model and year. That was the purpose of vacuum hose configurations, vacuum amplifiers or transducers and different vacuum ports. The difference in the valve itself had more to do with how they fit on the engine rather than how they behaved.
At any rate EGR clearly has a huge effect on NOX emissions and does completely change the way air and fuel burn inside an engine. That mains the entire way the engine is tuned needs to change to accompany the changes that EGR creates. For the most part EGR is beneficial. It is a lot like getting an octane boost (at no extra cost) and does allow for better fuel economy as well as overall better emissions *if* the engine is tuned to accommodate the changes in burn characteristics. That means changing air/fuel ratio as well as timing. The modern vehicle's computer takes care of all of that for you so yes you can get along quite nicely with any knowledge of it.
-jim
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