dont forget a TK test aswell, it'l let you know the condition of the headgasket although its unlikely to be the cause as the most common sign of a blown head gasket is tonnes of white smoke/steam right on start up which goes away and slightly difficult starting first thing in the morning, or if its bad enough commpression leak into the cooling system which is fairly obvious but from what infomation you've given its obviously not that bad. from what i can see its possible to be a leak from the turbo, possibly from the turbo cooling galleries may be leaking into the exhaust side, i dont think it'd be oil as oil creates a blueish smoke.