Ok so I have an update!
After I ran a tank through the Chevron fuel cleaner additive I got in terms of:
(1) Mileage : 354.6 miles and filled up next with E0 87 octane fuel at 12.02 gallons;
(2) CEL or knocking issue: None. Using Torque, I haven't found any hidden issues.
(3) Chirping occurred after startup +10 minutes at a standstill. If I operate the car after reaching warmup temperature, I found it chirps on and off depending on whether there are sustained 95-97 degrees C on the oil temperature gauge in Torque (this happens when sitting in traffic). On my 16.5 mile drive from home (Waipio) to work (University of Hawaii), without traffic I have no chirping, even when parking and sitting idle for some time.
So this may be a temperature issue. Perhaps as temperature rises in the engine bay, the rising fuel vapor pressure pushes the fuel pump ECU to operate the pump faster (and hence chirp?). This is all conjecture as I have not installed Techstream to decide if the fuel pressure ecu does anything I said.
EDIT: With E0 fuel, I feel as if the chirping is less evident. It does chirp when the engine oil and coolant level temperatures are sustained. After startup +15 minutes chirping occurs. Yay?
I have filled another tank of E0 87 octane (12.42 gallons after going 372.6 miles). Ill let you know if any more weird oddities pop up and if I get Techstream going.
