Performance chip tuning as a business can be very successful. There is no doubt that it works in so far as some cars gain power and in general don’t appear to suffer any side effects, or at least not many obvious ones. Lately, I have noticed some tuning companies offering economy tunes as distinct from power ones. In any one engine, e.g. for a given part load cruise, there should be just one level of fueling that will give maximum efficiency. Maximum efficiency should give both maximum power and maximum economy.
Can the manufacturers mapping really be that far off ideal? I wonder if the power tunes are on the upper ragged edge and the economy ones the lower (lean) edge of right?