I've read through this thread a time or two and have yet to determine what it is on these pump internals that can be "breaking in" and not only changing its' operation, but changing a it substantially. A few comments that maybe someone will clear up my misconceptions on...
How can anything be breaking in, which is simply another way of saying wearing in, when it is touted as having undergone a special manufacturing process to achieve superior Rockwell hardness to eliminate premature wear and is manufactured to a tolerance of .00005". I haven't had one apart, so educate me; it looks to me like four machined pieces of metal that work/fit together. What is there to wear in/break in? My only thought is that their claimed machining tolerances are somewhat optimistic. Again, I am not trying to ruffle any feathers, I'm just looking for technical explanations as to what is happening. I sent an email to PTP today asking about it and got this in reply:
"Every set of internals new to be broken in properly even with the tolerance
on the internals. It just a standard process to insure that they get worked
in properly. When you order your internals we do send out directions on how
to install and how to break in your fuel pump.
Thanks," To me it reads that when I asked what on the fuel pump parts need to be broken in, they tell me the pump parts do. Thanks, Captain Obvious.
How can the fuel pressure supplied by this pump not even meet the OEM pressure output when it is new? Seems some of you have shown very low pressures when new, then getting better as it breaks in. See #1 about what break in means.
Is the "fuel cut" being talked about as sharp as it is made to sound? I have had the occasional blip in performance of my car now and then but was only for a portion of a second then back again, and not at higher RPM/fuel requirement times. Why wouldn't Mazda would have put a soft cut in here rather than a total shut down?
Reading and learning, but that of course just leads to more questions. Thanks to everyone that helps us newbies make sense out of this stuff.