Chasing down the 5500 RPM stumble, still.
Ignition all looks good.

I put a fuel pressure gauge on the rail and this is what I get.

37# FPR connected
45# FPR disconnected

The fuel filter was changed a few years ago, although I think that might be a good starting point. The pump and the FPR are all origional.

Is my pressure normal or too low?
Any advice?

 

The standard operating pressure (no vacuum line) is 43.5psi. GM accepts anything form 41-47psi. When you attach the vacuum line, fuel pressure will drop proportional to intake manifold vacuum. With a stock cam, 6-8psi drop from the "no vacuum" reading is normal. With a larger cam, you'll get less pressure drop.

You need to measure the fuel pressure out on the road, with the engine near max RPM/max load. You should see at least 40psi under those conditions.