96 olds lss fuel pump issues maybe

96 olds LSS 3800 standard-185K -at highway speed starts slowing down as if running out of gas-intermittent. After slowing down or sometimes having to pull over, it sometimes shuts off, but not always. If it shuts off, upon restart it acts like it is out of gas, but then after a 5-30 minute wait, will restart. Upon restart runs rough, but then smooths out as if everything is fine. I think maybe fuel pump. fuel filter replaced 1 mo. ago. thought it was fixed, but repeated same thing twice last week. It is better though. It does not all the way die, just runs rough when it slows down. Able to keep pushing accelerator and it eventually comes around and smooths out.
Question? How do you determine if fuel pump is bad? Any thoughts appreciated!

You'll have to atatch a fuel gauge, tape it to the window, and drive it until it acts up. If the fuel guage drops well below 35 psi (ruffly) than it is indeed a fuel pressure issue.

Agreed. First diagnostic step.

Fuel pressure for this engine should run 48-55 Psi... At idle 44-45 will be normal.. If you are dropping to 30-35 you have issues and may need to change the pump..

If you find thats the issue, and want to replace the pump i hope you don't have a full tank of fuel... It takes a bit of work but its not a horrible job.. And you'll be surprised to see the size of the Pump..