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and many will ask, what specifically is this epa reg that will lower efficiency and raise cost?..

I believe this refers to Tier II emission standards being applied in October of this year rather than in 2004 as originally planned. This is as a result of a consent decree signed by the DOJ, EPA, and the heavy duty diesel engine manufacturers back in '98.

It seems that the silly lawyers in Washington D.C. wrote some emissions regulations a few years back without understanding current and near term engine control technology. Some enterprising engineers at Cat, Cummins, Mack etc., implemented the regs in such a way as to maximize fuel economy at the expense of NOx emissions in engine operating modes not explicitly covered by the regulations. I guess it was assumed by the EPA that if they defined emissions standards at multiple engine operating points, the emissions performance would interpolate between the points. That's the way mechanical fuel injection systems would have worked. I guess no one ever bothered to do any research or even pick up a few copies of Diesel Progress. Apparently they missed the advent of computerised electronic fuel injection and engine control. Pin heads.

"I believe this refers to Tier II emission standards being applied in October of this year rather than in 2004 as originally planned. This is as a result of a consent decree signed by the DOJ, EPA, and the heavy duty diesel engine manufacturers back in '98."

Thank you Data, now please search and find a way to defeat the democrats in all elections in the future.

You probably feel the same way I do about a consent decree between two agencies that have nothing to do with the trucking industry, or maybe better said, should have nothing to do with the trucking industry. Where are the industry folks, engine makers, trucking companies, etc. I know, it's a rhetorical question.

Some enterprising engineers at Cat, Cummins, Mack etc., implemented the regs in such a way as to maximize fuel economy at the expense of NOx emissions in engine operating modes not explicitly covered by the regulations."

That is certainly a diplomatic way of describing what the engine mfrs. actually did - they devised ways for the engine control strategy to provide low emissions ONLY during the emissions test cycle, but not during actual highway operation.
Then they got caught.
The victims in this little morality play, unfortunately, are the truck builders and their customers, the truck owners and operators.

BTW, when I wrote "engine mfrs" above, "mfrs" is NOT an abbreviation for "manufacturers", but for something I dare not spell out here.
(Peterbilt powertrain engineer,"redbob")

Apparently they missed the advent of computerised electronic fuel injection and engine control. Pin heads.

All is not necessarily lost -- there might be a loophole. The whole situation is based on the software in the engine computer. To satisfy EPA regs, the computer that ships with the engine has to control engine parameters so as to minimise emissions, at the cost of fuel economy.

You can reprogram the engine computer (called the PCM - Powertrain Control Module). One guy explains how

So, the aftermarket produces a bunch of ROM chips for these engines with revised software. Swap out the "EPA chip" for on-road use, swap it back in before getting emissions inspections...