1995 325IS Oxygen sensor help

[lasmariaspr]

I purchased my E36 two months ago, before I left with the car, the previous owner mentioned the OS. He said that when connected( By the way, No CAT on car) car would run fine without check engine lighted up. The OS is new, barely 2 months old. But , car would once in awhile stall like it was choking on gas, you couldn't press gas pedal in that moment, and it would resume normal. I have tried the car for a couple of weeks with OS disconnected, more gas consumption, you can smell the lean mixture, but no stalling at all. I really don't know if a new OS will fix this issue. Please advise!