There is no vacuum such as you have with a gas engine. It is just the crankcase vented to the intake, where the air flow pulls it into the engine to be burned during combustion. The later 1.6's had the fitting at the manifold downsized, to prevent engine run-away in teh event of excess blowby. (Oil is fuel to a diesel, remember.) You can just connect it to any pport on the gasser intake, won't matter.