Secondary ignition. Check your plug wires and especially the plug gap, but if you have them out might as well replace them if they are old.
Over time injectors tend to “foul” in their port, lower percentage but why not run a can of injector cleaner through the tank and see if it makes a little difference, if it does think about having the injectors cleaned.
Fuel pressure symptoms are pain and can be dangerous to diagnose if not done properly. You should have 45 – 50 lbs at all times otherwise the injectors wont “fire”.
Installing a fuel pressure gauge without the correct banjo connector or improperly can result in a fast all consuming fire by the time you grab the fire extinguisher

your car is gone, and the building you’re working in too. what fire extinguisher?

The gauge needs to be installed where it can be read at driving speeds too.
I would go after the secondary ignition components first.
Good luck.