He's basically saying that a standard one rises at a known rate...as your manifold pressure increases...

so say with a standard reg set at 3.5bar...the manifold pressure rises by 1 bar and the standard reg is now working at 4.5bar.

On an aftermarket one if the rate of increase is different you may see 5bar/4bar/4bar/6bar or whatever fuel pressure at exactly the same point.So you would need a remap once it's fitted to check it out.

oh and the standard regulator is very good, it works absolutely fine well past 20psi on any turbo!

i'd advise you to keep it