1994 Nissan Pathfinder

I have a 1994 Nissan Pathfinder XE automatic 4 x 4, Last month going up mountains enginge quite. Started after about 4 minutes but randomly quite. Limped back to town. Replaced fuel and air filter, spark plugs, had injectors pulled and cleaned, had fuel pump replaced.
Ran ok for one month. Now doing the same. Satlling wether I am going 55mph or 5mph randomly. At idle never stalls. Pulled fuel pump yesterday to inspect fuel in tank. Looked good no visible contamination. Plenty of gas at fuel filter when ingnition on. Checked the Dist cap and rotor a little worn but not dirty doesn't apper to have cracks.

So now I need to think maybe measure fuel pressure, to check pump what should it be?
Fuel pressure relay?
Fuel pump relay?
Mass Air sensor?
etc. Etc.
The problem is I live in Costa Rica in a fairly remote area. Good mechanics are a joke essentiall don't exist.
Any help would be appreciated

GM Costa Rica