I wouldn't consider myself an expert as I've broken more engines than Eddie Irvine. However, for what its worth, the VRO was designed to deliver a variable amount of oil according to engine revs. For some reason, probably reliability issues, a lot of people chose to disconnect this function. I ran a VRO50 on a 4metre Avon and the oil supply had been disconnected by a previous owner. This also blew out white smoke which made me think it was running lean. I noticed that the oil feed pipe into the carb,which had been disconnected from the VRO supply in the fuel tank, was not blanked off. When this was done, the engine ran a lot smoother, started easier and had a blueish tinge to the exhaust smoke. This was then run on a permanent mix of 50/1 with no problems.