02 sensors are original. The only thing that has ever been done to this van is an alternator (used), water pump (new) and plugs & wires, I just did those about 1k miles ago. Everything and I mean everything is all original. Oh yeah Except the tires LOL CV axles, tie rods, all that original. Well I thought the o2 sensors did really start registering until it ran for a certain amount of time? Doesnt it bypass their signal until they get to a certain temp? Unless they are heated? As far as the rocker arm van, "Harpo" on here had the same problem, and he has been through **** and back with his heads and pulling the motor out.. I think my valve is bent from it so I am pulling my head soon to see.....