Closed loop and open loop but regardless if he does not have O2s his car is going to run like ****. 87-95 cars have two O2 sensors, 96-up have four. Just get the Densos from Rockauto and call it good. Don't buy them locally for $75 a sensor or whatever the hell they charge.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.