The vehicle at issue is an '88 base Firebird with a L03. Symptoms included erratic idle, bogging down under 2000 rpms, and what seemed to be a miss in all gears. Replaced fuel filter, PCv, crankcase filter, fuel pressure diaphragm, TPS, IAC, spark plugs, spark plug wires, coil, distributor (including cap and internals), and questionable vacuum hoses. Re-timed the engine. Injectors and connectors were new and the symptoms remained unchanged I decided I should inspect and rebuild the throttle body and found what I though was some buildup in my passenger side injector pod where the fuel enters the pod, I pulled it out and examined it and this is what is was. Replaced it and put the parts back together and the problem is gone. Feels like I got a new motor under me. Just in case it helps.

 

The photo needs to be cropped at minimum, re-posed with the camera closer would be better still. Maybe you need to include a section of tape-measure or a coin or something to provide a sense of proportion/size/scale.

Far as I can tell, you're showing the pressure regulator diaphragm. Is that correct?

What was the "buildup" in the passenger side pod? Fuel deposits? Debris from the gas tank?

 

Fuel injector filter.