It sounds like you were standing right there while he was tuning your bike, did he use "Flash tune" to do it or some other program?However, it is the low rev ranges where the emission maps run far too lean and need to have fuel added. Exactly the area where the lambdas function to try to lean up the map again! Ideally the air/fuel ratio should be between 12.5 and 13.5 at all times. When we did the baseline run before flashing my bike the lower rev areas were reading 15 a 16 and at one point were off the chart too lean. If you look at my graph you can see that in most areas now the A/F is within the 12.5 to 13.5 parameter. If the lambdas were still functioning they would be trying to lean out the AF outside the parameters again because that’s what the emissions rules dictate.