I found the snorkel to be a restriction ages ago. The airbox on a GTR shouldn't be compared to one on a GTS-t or Stagea, which is where a lot of that information comes from.
I would also suggest that the turbine will shit itself in its own good time regardless of whether you are running 10psi or 12psi or 14psi. I am not arguing the science behind what makes them fail but history has shown that some fail with little or no provocation and some are flogged repeatedly and won't die. Regardless, on an RB25 there is little risk of engine damage (unlike a 26) so drive it till it fails.