There is a plastic,flat black,filter looking thing,that my fuel lines run through,on driver side,bolted to the frame, what is it? Can it cause fuel restriction?

 

One or two tank?
This may help:
Attachment 280309
Are you sure it is a 1990?
Because a 1990 should have this set up:
Attachment 280308

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Are you sure those aren't brake lines... sorta sounds like the RABS module. There should not be anything inline with the fuel lines on your truck unless it hsads one of those silly aftermarket devices that claim magic fuel savings but really do nothing at all.

 

My system is the second diagram.
Two fuel tanks,switched on the dash electricity,pump in each tank,no third pump,no mechanical valves,return lines to each tank. Under driver's seat (near the rabs) hanging away from the frame from a flat metal bracket with fuel lines going through it. That price is what my question is about. Again thanks to anyone who responds.referring to second diagram it would be between fuel pressure test port and fuel filter.and no after market parts,it very much looks original.

Ok

 

post a picture

 

Ok picture sent.
the problems that I'm having is, with 38lbs fuel pressure at the rail idling,under a load it seems like I'm not getting fuel volume,pinging,lack of power,lean bank code,no differential between switching tanks, new filter and front pump assembly.

 

Just a holder for the lines.

 

That is nothing important… might just be a splice connector or a hanging bracket. Looks like it might split apart if the bolt is removed, easy enough to find out.

That is actually to high, it should be more like 32psi idling with vacuum connected to the FPR.

What are the exact code numbers?

 

Without rechecking codes I forgot the number I just remembered one lean bank which indicated o2 sensor which at the time,I figured I found the problem,replaced the o2 sensor,check engine light never came back on,but this problem seems like it is getting worse,like its slowly starving for fuel,again same no matters which tank I'm on.

 

There aren't many codes that actually indicate an O2 sensor failure including these lean codes because the computer couldn't tell if the mixture was rich or lean if the O2 was broken. Given your description it sounds like the motor is running lean or is restricted but it's probably not fuel pressure related. Are the cats original? Anything that sounds like an exhaust leak? A broken air injection hose can cause an extreme lean condition and of course a partially melted cat will cut into performance.