Passenger may not have a removable doughnut.
Fuel injection engines really like no exhaust leaks. Some how they draw fresh oxygen into the system, tossing the readings out the window and confusion ensues
The added oxygen getting to the O2 sensor makes the computer think it's not getting enough fuel. It effectively fools itself into thinking the engine is running lean. So it adds fuel to compensate, but it never sees the mixture go back to the rich side. It can never overcome the lean condition so it continues to dump fuel. It will foul plugs pretty quickly.You know, that is super encouraging to hear because it's consistent with what @Capt Ron and I found when he came over last time. Engine was flooded with gas. If fresh air was coming in, it was probably throwing off the computer like you say. Pumping too much gas in and flooding itself.
Someone failed at that install. Try a long 3/8ths extension deep socket. wobble extension would be ideal @ 18 to 24" long. when you put it all together tighten each nut a little at a time alternating till each stud until tight. A little gasgasinch will help hold the doughnut in place so your new doesn't end up looking like that old one
Have the leaks at the exhaust manifolds been addressed?
If you feel the terminal snap on the plug tip your good

Is it TBI?Well, one of my injectors isn't spraying fuel. "There's your problem..."
I swapped the connectors and the same side still was not spraying, so it looks like it's gummed up or something. If anyone has tips on cleaning let me know.