Need more info, type of stainless, thickness, etc...

Do you mean 98 Ar - 2% O2 (oxygen)? This mix works good, but the welds tend to look poor due to the black smut that forms as a result of the presence of oxygen oxidizing the chromium in the SS. Typical Argon CO2 mixtures would be 95 Ar - 5 CO2 and 90 Ar - 10 CO2. Are you running spray transfer or short arc? This will also affect gas selection. I would suggest talking to your supplier as they should be able to help you.

Have you looked at FCAW? The operating characteristics are good and the slag peels easily if the weld is put down right. The welds are shiny after the slag is removed and have a smooth ripple pattern.

Regards.

98%Argon/2%CO2 is an ideal gas for MIG welding Stainless Steel. You will achieve a cosmetically good finish similar to Argon/Helium gas mixtures but at a fraction of the price. The welding arc will also be better than Ar/He mixes ( my opinion).
The only percieved problem is with dilution of the Carbon in the CO2 which may increase the weld metal carbon level above the accepted norm. eg .03%. Normally this is not a problem as most Stainless Steel are well below .03% anyway.
If you are uncertain do a test weld analysis.

look on the box the wire came in this is should be your best gas. I spent a lot of time trying to get a better gas along with a lot of headaches, and now am going back to the gas i started with which is 98%argon and 2%o2 for welding stainless, short circuit and spray.