Sometimes we've little things adding up. Others, it one issue.
Is your 4.7L 2UZ-fe, a VVTi? Does it have the S.A.I. system?
That one weak cylinder, could account for balance BK1 to BK2. With more going, also. Typically, when we talking % in a compression test. We're talking about leak down %. It best to list each cylinders PSI. What are the PSI readings for each?
You state: Fuel Injectors are "fine". How do you know this?
I like to look at LTFT & STFT, while cruising on HWY. No change in gas pedal, no hill just nice level HWY cruising. I log with my smartphone, VIA wireless OBDII. In logs I record FT, CAT temps, IAT, ECT, RPM, MPH and AT #1 at miniums. Then I look for points in data stream, where RPM & MPH steady (no change). This tells me when, I'm cruising steady at HWY speeds. That is where, all system at optimal or should be. Do you have data from when cruising?
+LTFT above 5% ( i see most LTFT~3% here in mile high city) indicates engine running lean. ECM is increasing fuel to mixture, to get STFT near 0%. Either fuel starvation or vacuum leak is most common, for high LTFT. In your STFT2, it is correcting to much or snap-shot to short duration, to be meaningful. This is where logs are really helpful.
We I do vacuum test with a gas, NAPA, propane, etc. I, just watch/listen to RPM. I suppose you can watch FT. But data, takes time to get to reader. You could pass over vacuum leak, and not see it on read out.
I've one case, where rust from fuel station old steel tanks. Was in gas tank, fuel pump sock and fuel filter. Resulted in reduce fuel flow. Fuel PSI checked out to spec. But fuel flow, apparently was not.
I've seen many improve, with new MAF sensor.
One easy test, swap A/F sensors. See if FT balance moves to BK1 being the worst.
