The egr valve has been around for quite a while now. My Honda had one, and yet still got 72 mpg on the highway. I would still have it today, if not for some car thieves who stole it from me.
Cars are a little more fuel-efficient now due to many things that have come around over the last several decades- synthetic oil products, fuel injection, vehicle weight reductions, and technological advancements from the Japanese auto companies.
The technology exists right now to get cars higher mpg, yet the Big Three auto makers here in America simply don't have the collective smarts to make it happen.
This is why they are going broke and laying off tens of thousands of people. Just take a look at GM. They are no longer the #1 car maker in the world. This is because of terrible and inept leadership at the top. They still make cars with very poor fuel efficiencies, despite higher gas prices, and the available examples from Japan.
Also, take a look at the fuel stats from the Japanese auto makers of Toyota and Honda. They ALWAYS best anything that is comparable to what America puts out.
That is because they are always looking for ways to save the customers money, as opposed to Ford, Chrysler and GM, who are more concerned about making high horsepower cars that only get 15 mpg.
They are still marketing their cars with what I call the "Red-neck" marketing agenda. That is, market and sell your cars because it goes from zero to 60 in 3 seconds, and it has a "hemi" under the hood.
This is why they are not selling many cars these days, and why the Japanese car companies are.
As far as Hybrids go, people are now finding out that the supposed high mpg's that these cars were getting was nothing but a lie and exaggeration. Now these poor saps are finding out that it will take them almost 30 years or so to finally see a return on their initial investment from the extra $7,000-10,000 dollars that they had to spend to get a hybrid.
They would not need to if our government had the guts to mandate that ALL cars get 40+ mpg like they should. All cars can get this, because Honda and Toyota pioneered this technology almost two decades ago.
Even my 2003 Civic EX Automatic- which is NOT a hybrid, gets 44 highway mpg, even with all the added exhaust requirements that you speak of.
In fact, my car is very fuel efficient, and it has almost ZERO exhaust pollutants.
Having tough federal emission mandates and high fuel mpg's are NOT
Both Honda and Toyota proved this decades ago.
It is the government's job to see to it that it can find solutions to the many problems that we face as Americans. They are not doing that now, and this is why we are seeing more of a threat to our economy and way of life by those Muslim Terrorists who wish to do us harm.