It is possible. At the risk of expanding on what Bob is telling you, I'd put it more simply: The likelihood the computer is the sole cause of your excess fuel is on par with the likelihood of any shop to accurately condemn it without swapping it first. Not very.

Added to the equation is his insistence on you purchasing one from him and his installing it for calibration. Just isn't so. After telling me that, I'd run away fast. Or insist he buys it and you watch him put it in and "calibrate" it.

--
Art Benstein near Baltimore