its not just getting the cars to pass the actual test. it is possible to get it to pass with out anything but in california it is different. also the way maryland measures its HC, co and noxs looks different. they measure parts per million in california. i dont have a sheet infront of me but i belive the hc max is around 65 for 15mp 45 for 25mph. which alone is a hard number to beat with a properly running DE. california cars were never designed to pass the emission test values they have to now. but that is the state trying to push "high polutant" cars off the road.