Chased my ass for a month last year, and figured out that the top half of my STBD TBI was not operating properly, swapped my PT TBI to the STBD motor, and it ran perfectly. I rebuilt the damn thing before I put it on the STBD motor, which already was running poorly. Over the winter I completely disassembled the upper end of the Port motor, found a bent push rod and three leaky valves. Fixed all that nonsense, put it back together, and had the same intermittent stall issue that the STBD motor had the year prior. Re-swapped out the upper TBI (that had been rebuilt with new gaskets, and new injectors), and BOOM, ran perfect...

So, now I know that I have an issue with one of my TBI units, but I can't figure out what it could be. The unit was rebuilt with new injectors and new fuel pressure regulator (diaphram and spring), and still won't stay running. Motor runs for 30-45 seconds, then starves for fuel, as fuel pressure stays constant.

I'm at a loss... could there be something wrong with the casting? I leave the base of the TBI in place, and all sensors, fuel lines, filters, etc., and swap only the upper part of the TBI with the two injectors, with brand new injectors, and brand new regulator, the thing still acts up.

Any idea what could be causing the issue? Is there a breath hole somewhere that should be cleared out? Some casting issue or passage issue that I should be aware of?