EGR is the root cause of the GDI carbon build up issue. Diesel engines have always been direct injection and they only started sufferering carbon build up since EGR was introduced.
The oil catch tank thing is a fashion fad and only exists because they are used on track cars. On the race track dropping oil on track is a major issue so the regulations demand if the engine crankcase breathes to atmosphere it must have a catch tank.
It is a bit like strut braces that were developed for forrest rallying they don't really do anything outside serious competition but easy to fabricate and sell at a profit.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I agree with Andy to an extent. While running, Ford DOHC valve covers are almost completely full of oil. This results in a lot of oil in the pcv system and oil will puddle in the intake manifold. If you see something like that, a catch can is necessary.
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