Hello valued Ranger experts.

I am a wheelchair driver. I have a 98 ranger XLT 4.0. 300,000 miles and going strong. Regular maintenance.
My check engine light has been on for over 10 years. Running solid with check engine light on.
Retired with limited income. It is my only independent transportation. I need it to have quality of life. I reside in an assisted living facility.
Decided to address problem.
Codes PO171 and PO174 too lean. I have changed intake manifold gaskets, valve cover gaskets, MAF and all 3 o2 sensors. EGR, Idle control, and PCV valves. Fuel pump, power steering pump, NGK plugs and wires, and oil change. Mechanic checked for vacuum leaks and found none. Drove, and check engine light came back on after 17 miles. Any ideas?
Was told maybe check engine light ingrained in computer and to drive for 2 hundred miles. I am very frustrated and can't afford a new or used vehicle. No dents, and Betsy is still running strong. Too lean code keeps coming back on read out. If you have time, could you please advise.

My Betsy.
Mechanic taking my limbs already. You are my last hope. Thanks for any suggestions you may have. After downstream o2 and EGR change rough idle. Idle relearn is what needs to be done now. Check engine light going to bankrupt me. HELP!!!
Stain on ground is not from my Betsy.

 

So if the light is coming back on, the problem still exists. Did the mechanic use a smoke machine to check for vac leaks? It could also be a fuel system issue. IE low fuel pressure, faulty injector on both banks,

What if any diag work was done before loading the parts cannon ?

 

Can a faulty fuel regulator be the problem?
Is it located in tank. I had new fuel pump installed.
Only diagnosis was check engine light scan and spraying to check for intake manifold leaks. Intake leaks confirmed. No vacuum leaks detected when checked after intake gaskets changed. Don't know if he did smoke check for leaks, but he said he confirmed no leaks. Only other thing right now is small leak from oil pan. Is it expensive to replace injectors? Do you think injectors could be the real problem seeing as I already changed everything else? Would hate to do injectors and still have problem. Last scan only showed one bank lean as opposed to both.
It was an O'Reilly scan.

 

IMO you should find a reputable shop and pay them to diag it. Tell them what was done and why,

More often than not you come out ahead by doing it that way vs firing the parts cannon and hoping something sticks