Nissan Repair: 1995 Nissan Pathfinder loses power, mass air flow sensor, mass air flow

Question
I have a 1995 Nissan Pathfinder.  It loses power even if you are going fast. I have also noticed that it doesn't seem to lose power as quickly in the morning as it does after it has been driven.  I have replaced all spark plugs and spark plug wires, the mass air flow sensor, fuel filter, fuel pump and distributor cap.  I have been told that I need a new fuel pump, but I think it may have something to do with the wiring.  Have you heard of this problem with this vehicle and has any of the wiring had to be replaced.  I am looking for the most economical way to diagnose and fix this problem.  Thank you in advance for your help.

Answer
Ken,

First I would check the fuel pressure to see if it drops off when you are driving and the vehicle looses power.  If the pressure goes down with the power then you know it is a fuel pump.  I recommend dealer fuel pumps as I have had trouble with aftermarket units.  If the pressure is fine I would be lloking at the dirstibutor for the optical pickup being contaminated with oil or the coil is failing.  You can check the coil for output when it is cold, in the morning and after the vehicle has been run.  If the readings are different then the coil is defective and the windings are failing.