I have a persisitant check engine light on my 99 legacy, I had Autozone check the codes and they said it is the gas cap but I have made sure it is tight and the check engine light keeps poping back after being cleared. Some oil change wanted me to change the O2 sensor and fuel filter. Help

Second is the issue of bad smell once in a while from the subaru. It let's out some bad egg smell which goes away after a day but will come back after a few months.
Anyone please help

Rotten egg smell is usually catalytic converter orientated.

Anyone have the "Egg" smell and NO CEL? Our 03 seems to do this all the time. It usually comes after putting a load on the engine ( we have some fairly steep hills to our house and our driveway is steep)

It doesn't matter if we are gentle on it or punch it up hill to get home, the smell comes. Mileage has never been good ( around 17 mpg avg.)

Of course, the car has been to the dealer and they "cannot duplicate" the condition, yet I can do it every day pulling into the garage. As with the above answer, I suspect the catalytic converter is not right ( plugged up, broken,defective,etc.) The car has 24k on it.

Any suggestions? The car has never shown a check engine light.

Is it smart to change the cat converter or what is the wisest thing to do. It seems kind of awkward how the spark plugs are set on the legacy, changing them is not the easiest thing. I am planning to change mine and I think I will have to take out some gadgets.

If you have the right extensions and such it should be easyier to get the sparkplugs out. You can always remove the airbox and windshield washer fluid resevoir if you want some more space. I didnt though.