Thanks for the update. I'm sorry to hear you are still dealing with this issue.
The fuel ratio imbalance can be caused by a lot of different things. For example, low fuel pressure, air leak, faulty injector, and so on. Since it is on both banks, I suspect the problem is something that is causing an air leak on one bank. Don't laugh, but I have even seen a leaking oil dipstick cause this.
The 2196 is similar. Many things can cause it as well such as excessive fuel pressure,
Leaking or contaminated fuel injectors, EVAP purge valve stuck open, biased MAP sensor signal, contaminated MAF sensor, positive crankcase ventilation (PCV) system, and the list goes on.
I would assume the shop knows to check for these things, but anything is possible. You may want to mention my thoughts and see if they have checked those things.
Let me know.
Saturday, July 29th, 2023 AT 8:54 PM