PO172 98 Mazda 626 2.0

I have a 98 Mazda 626 with the 2.0 four cylinder and a manual transmission. The car has a difficult time starting, and you can usually smell gas. After the startup, the car runs fine. The engine light went on, so I went to Autozone and had them hook the car up to their scanner. PO172 was the code that the computer gave, which is "Fuel Too Rich" on bank one. My Hayne's manual said that it could be the oxygen sensors, so I replaced both of them. That did nothing. In the troubleshooting section of the manual, it said that it could be leaky fuel injectors, but they are really expensive for this car, and I thought I would post a question first. Can anybody help? Thanks.