Fuel pressure is hanging around 18 psi, which is down from a healthy 48-55 psi. Thus far I have replaced the fuel pump, filter and pressure regulator. The thing is, it is sporadic. I'll have full power, the next second (literally) I've got no power. It will idle ok sometimes, but not want to take off. Other times it will finally quit.
Any ideas what could be doing this?

 

It would help to have the year of 88. I would check for an intermittent short in the fuel pump wiring, or a bad ground.