This is interesting and I'm all for counter-intuitive facts, but can anyone provide a source to back up these claims and give details as to the exact difference?
The problem with the claim that "pollution increased with emissions regulation" is that you need to specify what pollutant you are talking about. Here is more of the story:
https://www.dieselnet.com/standards/us/hd.phpParticulate matter (black smoke that is generally bad for your lungs) went from 0.6 g/bhp-hr in 1990 to 0.01 g/bhp-hr in 2010
NOx which causes smog went from 6.0 g/bhp-hr in 1990 to 0.2g/bhp-hr in 2010
Unburned hydrocarbons went from 1.2 g/bhp-hr in 1990 to 0.14g/bhp-hr in 2010
SOx emissions decreased to near zero with Ultra-low sulfur fuel, CO emissions are down, etc. So basically, all kinds of nasties were reduced.
Now, there is no doubt these reductions came at the expense of fuel economy because of the various technologies used. This means that if you only care about CO2, then you can wistfully recall the 90's. The concern about CO2 is relatively recent, however, and 2018 or 2020 emissions standards are right around the corner.
If you think these emissions reductions were a bad idea, I invite you to go to a big city in any third world country still using old engines and take a big whiff.
Finally, Hedge_87 is right about the new stuff being in the shop more often, but this is part of a larger discussion about how vehicles are getting more and more complex/computerized in every way. Even your tires have sensors in them now.