P0171 chasing lean

I want to start with thank you to all on this forum. I am the second owner of my 2000 4wd AC 4.7 Tundra. I bought it from a friend who drove daily in 2007 with 250k on it. I have proceeded to use the truck for work and then chores, current mileage is at 457k. This truck is on original motor, trans, rear end and runs great-ish. It was the time to get smog check on my car and natural it threw a code P0170 right before. In the process of running to part store to get a few things, new MAF (because I’ve been cleaning for years). My truck gave me a slap in the face for my neglect. While at the store the drivers side door latch mechanism failed, locking me out. Got home and started my research and found this enlightening forum and launched my quest.

Found how to fix the door latch, although had to wait for good weather to cut back door shackle off, to access front door latch. Pulled mechanism apart found degraded plastic spacer that limited release action. Insert metal cir-clip tightening it up. FIXED. Thank you!

Of course while reading was enlightened to my neglect with my timing belt. Feared starting it to begin addressing P0171 issue. So followed guides here and replaced my timing belt with ASIN kit from rock auto. Had leaky valve cover gaskets so pulled those off and check valve clearance. After 457k miles found 3 exhaust valves to be eve so slightly out of spec. Elected to leave it and button up with a planned recheck at 500k. VC oil leak FIXED! Thank you! Buttoned up everything again with new plugs, air filter, oil, oil filter, fuel filter, coolant. Now finally back to P0171.

Pulled data from ODB fusion. Found long term fuel trim on Bank 1 AND 2 both maxed out and short term trim pushing further. Ironically the truck runs pretty well but sluggish on pick up with a little stumbling, poor power. P0171 come with a smorgasbord of potential issues that can lead to lean code. Found some vacuum hoses to be a little tired and fixed. Looking closer at ODB data, see LT Trim tracks with RMP increase decrease, probably not a vacuum leak. The degree of lean could mean exhaust leak before O2 sensor B1, That should be fairly loud, but cars is quiet and no significant exhaust leak. O2 sensors seem to be operating properly.

Today I finally borrow a fuel gauge from AutoZone and connected to front fuel fitting B1. Checked fuel pump resistor at 0.9 ohm @ 80F, high but warmer than spec (0.7 - 0.79 ohm @ 68F). Turned ignition ON, 0 psi and fuel dampener screw did NOT raise or move. Started truck, got 21 psi. Turned off, after 5 minute at 20 psi. While running pulled vacuum line off fuel regulator with no motor change or pressure change 21 psi. I want to say AH HA! Fuel pump.

What say you all, Fuel Pump? Have I diagnosed properly? What am I missing?

Thanks again to all who contribute here. It has lit a fire in me again to get greasy and learn my truck. It is a beast and deserves better, so I’m trying.