Any areas of the map when you DONT want mbt?

Its my understanding that in the tuning process, we are searching for MBT in all cells. This means optimizing Ignition timing, VVT cam timing to achieve best VE..ect. But is there any area of the map where we dont want MBT for ignition and VVT?

Obviously idle, redline, and full vacuum at decel are going to be tuned for different reasons, but im asking about the cells of the map that are used in normal driving conditions (area under the curve)

As you figured, there are many times you don't want to use MBT - under light running and even moderate loads it's generally best to run it a little lean. This, with the additional ignition advance that can be used, will help prevent 'plug fouling and give significantly - 20% should be easy to find and as much as 30% may be possible - better fuel economy which, despite people claiming "it isn't important to them" can be hundreds, even thousands, of potential savings that can be used on further work on the vehicle, holidays, or whatever. For the light running you should be aiming for "lean best power", or lowest BSFC (Brake-Specific Fuel Consumption), which is the most power than can be obtained from a unit of fuel (or vice versa).

This is an optional readout on some dyno's but is hard to figure if 'road tuning', so it's simpler to aim for a lambda of around 1.1 to 1.15 for those conditions and graduate to MBT when power is more of a concern.