The zzp 16 hp is on a stock motor but it is caused by the motor to be leaned out to make more power. On a tune it would richen up and make less power. If i am wrong please correct me
You have it backwards, best power is achieved when running richer than stoiciometrice (14.7 to 1/ 1.0 lambda).
Keeping it simple when max power is achieved it is know as MBT or Mean Best Torque. From there a Lean MBT and Rich MBT can be found (max power on the lean side and conversely the rich side) but both of these are richer than stoic, like 13.2to1 as an arbitrary examble or a # smaller than 1 on the lambda scale like .942.
Turbo engines generally run a little richer than MBT as the extra fuel is used to cool the cyl chamber and acts as an anti-knock countermeasure.
The term "leaner is meaner" is quite misleading as its actually the leaner side of rich but not actually on the lean side of AFR (in the conext of max power)
As for why the ZZP makes more power even thou its leaning out the fuel trim, I'm not entirely sure there are more factors than just AFR. But assuming they dynoed with the insert removed it would likely be the significant increase in airflow (and presumeably why it leaned out the fuel trims and would cause a CEL but at WOT its already running rich so maybe its close to Lean best torque). Just alil speculation
