Hey Benny, actually this is one of those 'old tricks' that I have seen
around for some time. The theory being that the relief valve spring becomes
weak, over time, relieving pressure below design, etc., I'm sure you know
the drill. Personally, this is one of those parts I replace with new, in the
event that I experience low oil pressure.
To get to the point, I'm pretty sure that one of the vendors we all commonly
use here in the US, actually recommends stretching the spring. I'm certain I
experienced this first hand recently. I tried finding them tonight, but it's
late and I'm going to bed. That is all. Gracias. Miguel