I have always added so injector retard in my tunes. It just makes sense when the engine isn't pulling much vacuum and you want it to enter the cylinder when the valve is open and drawing intake air.
Another point to consider is when the ECM is actually commanding the injector opening with respect to the crank reference angle. For example, on an XFI the injector pulses at crank reference angle. so if you want to retard the injector opening you must go more than the factory 10 degree refence. If your running in IPU mode at 50 degrees reference angle, the injector pulse happens at 50 BTDC and needs +50 retard just to get it to TDC and even more if you want it to occur when the intake valve is open further and pulling vacuum in the cylinder.
AG.
