The local GM dealer here(Vancouver) sells a product called
"Cleens" by GM.This is described as a "combustion chamber conditioner".When I asked about Delco X66 the guy said"this
is the same stuff". Part #992872 500ml cost me $4.25CAN.I am going to try it out on a '73 BMW 3.0 cs and will report the results.The instructions for use appear identical to what has been posted here already.There is not much in the way of precautionary language but that probably has more to do with the amount of space the French translation takes than anything else.