Trying to tune to ECU for more boost
Reply #18 –
I call BS. There's absolutely no reason for you to run lean on stock boost... they just want You to pay them to work on it. Ford tuned these things to run way rich. The only way to run lean really is if your pump is dying, and then it would be pretty obvious.
The o2 isn't even used under boost, so I would say that's not it..
Chances are your car is fine.