heavy breathing diesel

[diesel driver]

My 1.5TD is bog standard and goes like a dream, except that it has excessive compression into the rocker case, which shows as oil pushed out of the rocker cover gasget, despite the easy-breathe pipes I've added to the rocker case. But the car doesn't smoke, or guzzle oil, apart from what drips off the rocker gasget, so I reckon the bores & rings are okay (for a car with 170,000 miles on it).

Are there any pipes or airways which might be blocked causing this? Could I easily get at them to clear them? Any tips would be much appreciated.

[mowgli]

is there a breather filter fitted? because when they get a bit clogged, the crankcase pressure increases. or maybe a new rocker cover gasket it needed. diesels do breath heavier after a lot of use. where I work, there is a digger with an Isuzu td engine that has done loads of work and breathes a lot, but doesn't use any oil.