This maybe the case if your tuner knows what he is doing.

A tuner maybe able to dial in your air/fuel ratios by street tuning your car, however ignition timing is a little different. Some local so called "tuners" think they can read a few articles on the internet & look at other people's basemaps to learn how much timing to run. This works for the most part, but do they really know what they are doing ?

This is where experience & the importance of a dyno comes into the picture.