It could very well be a lean condition caused by a failing fuel pump. Highest fuel pressure that I read was 35 psi, after bleeding gauge. I don't know why I had to bleed the gauge and spray fuel everywhere to get the thing to read even that high. Fuel pressure fell to 30 psi while driving, but stayed there. I've read that fuel pumps can fail slowly, and not just quickly. Fuel pump whines loudly, engine surges for a few minutes at every cold startup, for about a minute. Is now doing the same surging, followed by a backfire. Not a loud backfire, but is still there.
