This is what Dinan had to say in an earlier thread about why the Dinan tune runs richer. The question is whether the OP's results are too rich.
Originally Posted by Steve.breen@dinan
Thanks for the comparison graphs, Kelvin.
The Dinan tune runs richer than the JB3 and stock because it's necessary to run a richer mixture when increasing boost. As you increase cylinder pressure by adding boost, the mixture needs to be richened for a couple reasons. The first is to reduce detonation, a side effect of increased cylinder pressure. Incidentally, the reason why the JB3 power curve is so lumpy is because the knock control system is actively pulling timing back in order to save the engine from detonation. The second reason for a richer mixture is to reduce piston crown temperature and catalytic converter temperature to ensure long-term durability.
Our tech article titled "Safety Strategies for a BMW Turbo Control System" is a good resource for more information:
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