[flybouy]

Seems like every time the EPA dictates new emission standards it takes the automakers a few years to make it work. The end of the 1960's it was the ridiculous smog pumps. Pre 1972 Ford 460 cid was like 365 hp, after '72 it was 220. Fuel mileage was also atrocious. When lead free fuel was mandated many cars had valve issues because the lead was the lubricant. I remember the original catalytic converters clogging up with regularity. Many garages would take a length of rebar and knock out the catalyst to keep the engine from burning up. When they started on the diesels the regen cycles were killer and created a lot of smoke, destroyed mileage, and often forced you to drive extra miles to clear out the issue or face a build of carbon in the particulate filter and costing thousands to fix.
As most government mandates I think the intent is good but the implementation sucks.
As for enforcement, again it seems to me the feds take the easy way out. I get that it,s bad to have a bunch of 18 wheelers driving millions of miles polluting but aren't there bigger fish out there? Seems like every heavy rain the Baltimore sewer system overflows and dumps MILLIONS of gallons of raw sewage into the Chesapeake Bay. Where's the EPA then? Last week the Delaware River bridge was shut down for hours because the "processing plant" beside the north end of the bridge released so much flammable vapors they feared explosions. On the west end of the Francis Scott Key Bridge around Baltimore the WR Grace company had so many white powdery cloud releases that they installed warning signs along the road with flashing lights to warn drivers.
I know this is long winded and my point is this. Not every diesel driver is running a tune so the truck looks like a steam locomotive but is just trying to improve a bad implementation of a good intention. YMHO