Two sets of standards have been defined for light-duty vehicles in the Clean Air Act Amendments (CAAA) of 1990:
Tier 1 standards, which were published as a final rule on June 5, 1991 and phased-in progressively between 1994 and 1997.
Tier 2 standards, which were adopted on December 21, 1999, with a phase-in implementation schedule from 2004 to 2009.
Tier 1 standards applied to all new light-duty vehicles (LDV), such as passenger cars, light-duty trucks, sport utility vehicles (SUV), minivans and pick-up trucks. The LDV category included all vehicles of less than 8500 lb gross vehicle weight rating, GVWR (vehicle weight plus rated cargo capacity). LDVs were further divided into the following sub-categories:
Light light-duty trucks (LLDT), below 6000 lbs GVWR
Heavy light-duty trucks (HLDT), above 6000 lbs GVWR
so i lucked out, the trooper is a 1993. 1 year before testing, therefore exempt? im not sure, but i found a cool web site Emission Standards: United States
i sea foamed the gasser. after i let it sit for around twenty mins, all kinds of smoke came out of that beast. couldnt even see the dirt road behind me. we will see if it get mileage back up. if it doesn't, its time to pay a little homage to Rudolph Diesel himself ! ! ! ! !