An Oil Catch Can was never designed for preventing oil/carbon build up on the intake valves. What it was designed for, and will successfully do, is catch the free floating oil vapor that usually gets caught in an FMIC, Intake Piping, Charge Pipe, DVs/BOV, etc. Obviously it's impossible to catch 100% of the oil vapor, but this will definitely catch a significant amount of the vapors.
Oil blow through occurs on every N54 from some degree, even completely stock cars. Anyone who's seen an FMIC be installed can confirm this just by looking in the end tanks or stock couplers, chances are there is some oil residue.