I'm not an attorney, but it's my understanding that tampering/disabling required emissions control equipment is a violation of federal law.

Correct.

The only legitimate use of O2 simulators is for off road / track use where emission controls are not required. Many people use them on race cars where the exhausts are modified and the car is not used on the street. In an ML, it is stupid, pointless, illegal, and a stupid way to hurt the environment (even if you are not a tree hugger).

nice write up for an off-road application. thanks!

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dan

After about a year, I got a check engine light. I disconnected the battery overnight to totally erase all the codes and haven't had any codes for a month. My research indicates that the computer may eventually decide that a cat has failed despite the simulator but this is a function of volatile memory. The truck runs on regular with no gas mileage reduction and I attribute this to reduced combustion chamber temperatures resulting from the reduced exhaust back pressure. Ordinarily, regular would cause some detonation for the knock sensors to pick up and the computer would detune the engine to protect it.