Engine Performance problem
1991 Cadillac Brougham V8 Two Wheel Drive Automatic 192000 miles

Is the fuel pressure regulator located beneath the intake cover or is it located behind the injectors in the carb. I am wondering cause I am trying to figure out if my car is running rich or if oil is leaking past the seals. I get the black soot out the exhaust and my spark plugs are fouled and they are carbon covered and I can clean them off and use them again. I just need help in figuring out if its oil in the cc or if its a rich fuel mixture. Please help.