Good morning all, I've got an '88 5.7L TBI in my shop that is kicking my butt. Everything seems to be in order but the truck leans out with basically any throttle input. It started out as a rough running/low power diag. Scantool data shows that the O2 sensor is going lean as soon as throttle is depressed. If you stay below 25% or so, it runs reasonably well, albeit pretty consistently lean. Checked fuel pressure and found it to be good. BLM goes high (172) but system just runs leaner and leaner as throttle is opened. Could see some pattern irregularities with the injectors so we threw a pair in early on. No change. MAP signal is good, TPS is good, ECT is good, RPM is good (all measured with scantool to verify good input to ECM. Finally connected labscope to injector pulse signal and found good solid signal on both injectors with no noise. However, it doesn't matter what conditions are present, the pulse width doesn't change. Frequency changes with engine speed (of course) but no change in injector on time. At that point, I thought maybe ECM trouble. Verified all powers and ground were present and then sourced a known good, used ECM and installed with no change. I feel like I am missing an input right in front of my face that would basically throw the ECM into "limp mode". That is what it is acting like. All of the inputs are there to cause the ECM to increase pulse width, it just won't do it. What am I missing? ANY ideas are welcome. Thanks, Joe