Sounds like your fuel pump is shot.

 

It has been replaced.

 

I would check the regulator if it's killing pressure off at WOT if it's fine then it's either an electrical issue or an ignition issue.

 

Well if pump is good and filter is good and reg is good then it sounds like you have a blockage in the rail. Wonder if you can blow out the lines with compressed air or you might have to route some alternative fuel lines.

Fuel pressure is supposed to hold around the level it reads with vac line off reg. If it goes to zero you have fuel problem and it can only be pump,filter ,reg or lines .What about blocking inlet screen on pump..?