Depending on what cams you have fitted you can get ome extremely good gains from these engines with a custom map as the overlap on quite wild cams totally ruins the airflow meters readings at high RPM and makes them go very rich. A good indication you have such an overlap is the idle going very lumpy.

AFM's are not good at autocorrecting for overlap due to various wierd airflow reversal pulses that they pick up on and incorrectly account for.