Having trawled the various (and sometimes acrimonious!) posts on crankcase breathing I wonder if anyone would care to comment on my specific set-up. I'm building a fast road 1275 (SW5 cam, ported head, twin 1.25" SUs) and I would like to use the Monza oil cap I currently have on the rocker cover of the 998 that's in the car now. These caps are vented to allow release of pressure when used on fuel tanks and to also allow air in. On the standard single carb 998 I put a filter on the tappet cover vent and that was the extent of breathers on that engine, which perhaps predictably leaked oil from various places.
On the 1275 I have a vent/can on the timing cover, another for the transfer case and a rocker cover with a breather pipe stub.
Would best practice be to connect the two cans to the carbs (with some form of balancer) and the rocker cover to the valve on the inlet manifold - presuming it's a PCV?