This is a very complicated subject. California truck owners are eligible for grants to update their engines. I drove this summer and my company does not go to California. Trucks and trailers will have to be aerodynamic. Reefers have to use DEF. Many companies will stop going to CA and just drop the trailers in Nevada where a compliant truck will take it into CA. MH's will never be part of this stupidity. However both CARB and the EPA will be cracking down on ALL vehicles that have modified their ECM's or are using non compliant chips. The fines for selling these contraptions will become very steep. BC in Canada is also considering fines for sellers.
Moisheh