taking this from one of the post you linked
discarding things
List of possibilities:
1 Fuel quality (low quality fuel a/k/a Murphy Gas)
2 Fuel quantity (filter or pump issue)
3 ignition issues (plugs, wires, coils injector flow)
4 temperature control (too high or too low)
5 vacuum leaks
6 exhaust leaks (not only an annoying noise, but it effects proper value reporting to the ECM by the AF and O2 sensors)
7 poor amperage conductivity (i.e. battery or cabling)
Sensor issues can be:
8 MAF (Mass Air Flow Meter)
9 MAP (Manifold Absolute Pressure)
10 ECT (Engine Coolant Temperature)
11 AF (Air/Fuel ratio a.k.a. Front O2 which can be a single bank 1 for 4 cyl or bank 1 or bank 2 H6)
12 O2 (This is the actual O2 behind the CAT that lets the computer know how the CAT is functioning)
Results:
1 NO, i did refill again with known and suggested fuel for this purpose, this time (a months ago i did use premium (93 although this car can run for regular, and in fact i get better mileage with regular) after that tank i used 89, then yesterday 87 again
2 NO, filter is new, pump too, both working good and with pressure
3 NO
4 NO
5 Pending to check, highly doubt it
6 Pending to check, although 3 weeks ago i did an extensive inspection underneath, and use to take photo of all the area to keep records (yes i keep a log of all parts, with parts numbers, details, descriptions and comments, maintenance and repairs or modifications done) and i didn't see any smoke mark of leak around the exhaust gaskets (the engine block is aluminum clean yet so it would have been easy to see) but i will check again later, although my mom asked me a week ago if there is a leakage in the exhaust, to notice, she are used to the H6 sound, the h4 for her is new, she even thought the car was bad because the engine noise and vibration lol
7 NO, new battery, a ground kit installed and alternator in good working orden.
8 SUSPECT
9 PENDING TO VERIFY
10 Pending to check, highly doubt it, since the reading in the dashboard and in the obd2 app match the actual readings of an infrared thermometer when measured manually.
11 SUSPECT
12 SUSPECT
i already ordered the filter box with the second "filter" carbon canister mesh thing, i got it for 30 bucks new on ebay... just to discard things
Advices please