I could see the off road being farm equipment.
They have choked these engines so bad that you now have to buy the next size larger machine than you had just to do the same job. Guys were ordering the same size combine and found out it had no power. Several places make black boxes to change the fuel timing. I am not sure how much that effects the emissions.

One huge problem that is going to happen is used semi trucks with emission equipment problems. They are a never ending problem and parts are really expensive. You cant put $2000 of parts on a 10 year old truck every 6 months.