We don’t know the codes. I noticed what seemed like a loss of acceleration at some point, but after a couple of weeks I convinced myself that it was my imagination, possibly because of getting adjusted to it combined with my wife not agreeing with my perception. My mileage remained in the neighborhood of 48-50 consistently, so my concerns faded. At some point the “check engine” light came on, but it wasn’t always on, just most of the time. And it didn’t come on upon turning on the engine – it always turned on somewhere between 100 yards and 2 miles of driving. Then my mileage fell to around 44-45, which also coincided with fall temperatures arriving. As I was approaching inspection time, I decided to get the “check engine” light checked, not really thinking it would be a big deal (in the past on my gasoline cars this has always had something to do with the oxygen sensor in emissions control). So all I know is what my mechanic has told me, plus an advisory I’d gotten when I first bought the car to not let a mechanic replace the turbo (major bucks) when most of the time the problem is a much less expensive issue with the wastegate. If it’s not possible to replace the wastegate without replacing the whole turbo, why would I have been given this pointer? Anyway, the symptoms are as I described – loss of some pep, followed by periodic “check engine” light becoming more consistent and coming on shortly after driving rather than at start-up, followed by a 10% loss in mileage.