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I havn't ran mine since I installed the headman long tubes. I could be wrong but I don't think it makes a difference on these old rigs. I have a 7.5. Someone who knows will chime in. I have no egr, smog pump disconnected, no o2 sensors.
1990 7.5
Without an O2 sensor the computer will run with default values. That usually means the fuel/air mixture is on the rich side. Since there is only one O2 sensor on "these old rigs" it is in your best interest and wallet thickness (rich mixture equals less MPGs) to have the O2 sensor in place to facilitate closed loop engine control.
A singe O2 sensor in the passenger side collector works just fine, I can go into details if anyone is interested but the short story version is that determining this involved some analysis using my Tweecer RT and tuner software. And "works just fine" means the EFI system will run correctly and maintain the proper A/F ratio.
I'm used to running 4 cylinder cars, so I get the jist of it. That said, if you want to get really high tech, you could run a stand alone ECU and put an o2 and EGT sensor on every single exhaust port. Expensive, high tech, not needed for a daily driver though.
But thanks for everyone for saying what I already searched and found out.
Cheers!