Thought I would update this thread after doing some investigation.
I ended up with a Mishmoto unit, it was on a special. Nicely made with an internal baffle and vapour filter.
My initial assumption was to fit the filter between the crank case breather on the block and PVC valve on the inlet manifold. With the peculiarities of the EFI system, it made sense to place it here as the line is open to vacuum from the inlet manifold under partial throttle drawing blowback gases back into the inlet to be burnt. Any oil and residue from blowback gasses should be collected in the can before heading back into the inlet.
Having run the car for several long trips with the catch can in this position, I got nothing but a little condensation. So back to the drawing board.
Next was to reposition the unit to pick up the blowback gases between the valve cover breather and the inlet pick up point prior to the throttle body on the inlet.
Under partial throttle the engine will draw fresh air through the valve case breather due to the vacuum present at the inlet manifold and expel the blowback gases that way. At full throttle however there is no vacuum in the inlet manifold and blowback gases will vent through the top of the engine through the valve cover breather and exit back into the inlet, so the engine eats its own gunk.
Again, ran the car with the catch can in this position for several long trips. This time there was about a teaspoon full of brown oily liquid. So a result I believe.
So the catch can has now become a permanent feature. Because the can is quite small it has been secured to the inlet manifold to keep the pipe runs as short as possible to stop the pipe bends filling with gunk instead of the can. Plus the can is easily reached in this position to unscrew and empty. Result is a cleaner air supply to the engine and cleaner inlet ports.
