TBI Engine is running lean. I suspect a fuel problem. Already swapped out injectors with known good ones, no change.
Measured pressure on the low side at 9, but it's steady.

When pinching the fuel return line, what behavior would point to a pump problem vs, what is a regulator problem?

I've seen people say that if the pressure doesnt rise with the line pinched then the pump is bad. While others say that if the pressure rises this is a regulator problem because the spring isn't able to control the pressure.

Which is it?