You have 3 zone, before the turbo spool, at spool and after spool.-Before turbo spool, engine run like NA, 15:1 to 17:1 is good, 14:1 between 1000 to 1400rpm for better torq if little smoke is ok.-At turbo spool, very narrow zone of rpm (200 to 600rpm zone), very hard to adjust A/F, 14:1 to 15:1 is better for fast spool, 15:1 to 17:1 for low cloud of smoke, many chip car are too rich in this zone but is very narrow zone!.-After turbo spool, 15.5:1 to 16:1 is good target, gray haze and good power, 17:1 to 17.5:1 is low smoke ajustement, more than 18:1 power drop fast but no smoke in most case.In exel, just divide air by fuel for A/F!But chip are not calibrate for quantity of fuel, if nozzle, head or voltage map are change, ecu report wrong quantity of fuel.Add O2 wide band on your down pipe and see what happen, i have and is very usefull for good tune.Dieseleux