I had a 91 LX 5.0. There is a splash guard blocking the oil filler shaft (for lack of a better name). When I put after market rockers on, they were taller than the original ones and I had to take the splash guard off. That meant that as the rockers were "rocking", oil was being splashed up the filler tube.
As for the breather going back to the intake, I can't recall if there was a splash guard there too. But if he has aftermarket rockers, it may be something to check.
Tell him to get rid of the breather and seal the crankcase up like it should be. Get a turbocoupe pcv to keep it from pressurizing under boost.
He needs to get on the Corral and search around, there's lots of things that could be causing it, under boost it will likely get some blowby though if it's got any miles on it.
Just curious, one of the local guys just sold a super nice coupe with a Procharger to someone down there, what color is it?