Question about the oil pressure. 1-2bar?
and then 3 bar max?
What meter are you using?
I'm using old omori mechanical, I see 2-3 bar after cold start, then 3-4 bar when hot. (my oil pump is new, now only about 50K km.)
My vtec engagement is 4.8-6K, variable vtec setting with s300, so I don't simply engage vtec at half throttle. 4.8K vtec only happens at full throttle.
If you suspect VTEC not turning on, uncheck the VTEC spool error check option in the s300. That disables the VTEC oil pressure switch, so it will turn on vtec solenoid even if the pressure is low. But whether the cams can lock the mid rocker with such low pressure is another question. If it's too low, VTEC engagement will be jerky or totally fail.
Oh, you should try the motul turbolite sometime, see if the pressure better or not.
Using the S300, you can datalog and check the graph to see if vtec solenoid turns on. I'll post a picture of a sample graph later, if I go out and drive.
Do remember that what the S300 reports is the VTEC solenoid turning on, not the mid rockers locking, so if you plug in a spare solenoid unconnected to the head, it will report the solenoid as turning on, even though your engine is running on low cams/primary&secondary lobes.
Common causes of low pressure is sometimes loose main bearings, apart from the obvious like failing oil pump.