Here's what I'm thinking: installing a brand new fuel pump, changing nothing else, might've over-powered the aged (possibly bad) fuel filter and new-ish Bosch FPR (since I didn't buy it, nor install it, it could possibly be bad or even a counterfeit part?), and the increased prssure from the new pump caused the instantaneous change from lean fuel trims to rich fuel trims. If so, and the fuel pressure readings show more than 50+1 psi (or much more, or even way under...though I think that's hardly likely), then I'll assume that I need another filter +FPR (leaning towards Hengst or Mann).

Do I even need to open up the left tank at this point?

The proven-good Siemens MAF hasn't out-of-the-blue gone bad simultaneously, and the O2 sensors, working fine in every test I've made (and working fine in the current series of photos I've taken of my dashboard display, in post #72 of this thread), haven't suddenly gone bad. Coincidence (even my luck with bad incidents coming in threes) doesn't quite occur like that, when only one component was changed.

I learned a lesson while racing & modifying my race car, that I should never change more than one thing at a time (from bad experiences doing the opposite).

__________________
01 BMW X5 E53,3.0i-5L40E, 7/13/01
topas-blau,Leder-grau,"resto-project car"

Here:
14 Lexus ES350,3.5L-U660E
09 HHR Panel,2.2L-4T45E
04 Chevy 2500HD,6.0L-4L80E
98 GMC Sierra 1500,5.7L-4L60E

Gone:
66 Chevelle Malibu 2dr ht.,327>441c.i.-TH350>PGlide/transbrake
08 Cobalt Coupe,2.2L-4T45E
69 & 75 C10s,350c.i.-TH350
86 S10,2.8L-700R4
73 Volvo 142,2.0L-MT4
72 & 73 VW SuperBeetles,1.6l-MT4
64 VW,1.2l-MT4
67 Dodge Monaco 500 2dr ht.,383c.i.-A727
56 Chevy 210 4dr,265c.i.-PGlide