L31MaxExpress
I'm Awesome
Given the fact the 02 sensor shows over 900 mv under throttle, it is not a lack of fuel issue. Do you have a known good distributor and coil to swap into this truck? Perhaps from the same truck that you tested the TBI off. I do not even trust new ones out of the box now.
Years ago I had a L03 F-car that was ******* down hard with throttle but would start and idle ok. Was messing around with stuff and spent several hours of checking things. What ended up being the issue was an aftermarket reman distributor. The pickup coil had been replaced and it did not have the GM style connector on it. The pickup coil was plugged into the module backwards. When the EST circuit was connected to the ECM after setting the initial timing, the timing was actually being retarded. For some reason that I still do not understand, flipping those wires made the timing advance rather than retard when the ECM was reconnected. After flipping the pickup coil connector, the car ran perfectly.
Years ago I had a L03 F-car that was ******* down hard with throttle but would start and idle ok. Was messing around with stuff and spent several hours of checking things. What ended up being the issue was an aftermarket reman distributor. The pickup coil had been replaced and it did not have the GM style connector on it. The pickup coil was plugged into the module backwards. When the EST circuit was connected to the ECM after setting the initial timing, the timing was actually being retarded. For some reason that I still do not understand, flipping those wires made the timing advance rather than retard when the ECM was reconnected. After flipping the pickup coil connector, the car ran perfectly.