Unsteady Power, System Too Lean Bank 1
 

I have an '01 9-3. About a year and a half ago, I took it for it's 90,000 mile service where they did a "fuel system flush." When I got the car back, it ran much worse than when I got it. At first, it was hesitant to even start. That problem seemed to go away, but the acceleration remained very jerky, and the power very unsteady/weak when I would hit the gas with some gusto. Also, if I press the gas and get the RPM's up to say 3000 then release the gas, it takes some time for the RPM's to go back down. Now my check engine light is on, "System Too Lean Bank 1." O2 sensors are good, think I've checked every vacuum hose I can see, replaced fuel filter. Any thoughts? Thanks!