Gas Smell while car is running

I have a 1991 oldsmobile cutlass ciera 3.3 liter v6 with 95,000 miles. I just recently had the gas tank, sending unit and fuel filter replaced. Just recently I noticed a strong smell of gas when the car is running, it seems to come from the exhaust. There is only a smell when the car is running after the car is turned off the smell is gone. Is it possible the oxyen sensor is faulty causing the engine to run to rich?? Any help with be appreciated.

I'll say first that it's more likey that your fuel line was disturbed during the work you had done.

As far as your guess, it is more likely that you would smell a rotten egg type odour if you were running to rich. Put on your crappiest shirt and lay under tha car while it is running and watch for tiny drops... it's likely you'll find some.

How long ago where the repairs performed? If the repair shop didnt notice, it could be either outright neglect or a case where the line was disturbed, but didnt rupture until later.

I'd guess they forgot to reattach the tank vent ,
or it was moved where the fumes could leach into the car.

Could also be the injectors "O" rings that seal them into the intake.
If they are bad, when its running, you'll see fuel spray out around them.