Smokin' at statup
Oil in the turbo inlet *may* be promoted by an early design valve cover and oil separator, but I've seen and owned XR4Tis with the original valve cover/breather design that never showed more than a trace of oil at the inlet.
Before looking for the redesigned top works or building a breather/separator, be sure to make sure your PCV valve is sealing tight under boost conditions and the breather separator is not gunked up or saturated.
The XR4Ti application is considerably more demanding than a regular PCV vacuum modulating system. I our cars, the PCV must also serve as a check valve and prevent any air flow from going the wrong way under boost conditions.
If the PCV leaks, air will enter the crankcase past the PCV. Where will it go? The breather/separator is the only open vent, so the air travels *out* the breather inlet...along with any oil vapors and oil splash in the valve cover.
Another thing that can aggravate this system is a dirty, oil saturated breather filter/separator. This black can with bronze mesh inside is intended to condense any oil vapors present and let them drip back down into the engine. If the mesh is dirty saturated with oil, it doesn't do a very good job and oil vapors pass right by. Where? Into the turbo inlet where they then condense back to liquid.
Clean the breather with a solvent. Most experts here on the list believe the OE Ford PCV valve is the only one that works.