Yes just the passenger side. Driver's side still works great. I checked the hose and nozzle and all are clear. That's why I figured the circuit board. But then again I did nickname this truck "Christine". Lol
The passenger side on my 90 Sierra stopped working several years ago. I'm sure it was the circuit board but I've just never got around to fixing it. Nozzle isn't clogged.
O2 sensor? My 90 started setting the CEL years ago only at highway speeds and only after about 5 minutes on the highway. I changed out the O2 sensor and the EGR valve. Problem solved. I noticed the O2 sensor was not listed in the parts you have changed.
How old is the battery and alternator? Have you had them tested? Also check and make sure there isn't any corrosion on the battery cables themselves. Even under the sleeves. My 90 Sierra 5.7l did the same when the cables were corroded under the sleeves. Replaced cables and problem solved.
I know I just put A/C Delco wires on my 90 Sierra with 5.7l. Never again. I had a hell of a time getting those wires onto the plugs and dist cap. Never had this issue with other brands. I am surprised I didn't break a plug doing it.
Now I need to go look at my truck. I have never seen one of those on my 90 Sierra. I am in Texas and I don't need to have an emissions test either since my truck is over 25 years old.
I know the auto parts stores sell a shorter belt if you don't want to go the A/C bypass pulley route. So the choice is yours. I personally put the bypass pulley on mine.