Im wondering if GM ever included a way to control when the injectors fire relative to TDC? I know in some of the old OBD 1.5 PCMs, there was a way to do it, but I have yet to find it in my 98 vortec PCM.
The reason I need to offset when they fire is that the cam overlap is literally just sucking the injector fuel pulses out of the cylinders at low RPMs. Basically as soon as the manifold vacuum decreases, the apparent AFRs just plummet to < 30:1 and the engine has a horrible hesitation. From what I can tell from teh mass airflow, the engine fueling should still be good, but the engine just goes dead lean at low RPMs and high throttle. Once it get above the RPM band where it does it, the AFRs return to whats commanded. I tried it in speed density as well, and its even worse.
It would be nice to delay each injector firing until the exhaust valve has seated so I dont loose all my fuel out into the exhaust. Id rather do this than just use the VE table to drown it in fuel until the problem goes away.