If you haven't done it lately, you should clean the throttle body, do an intake manifold cleaning (using chemicals through the intake without removing the intake manifold), and add a bottle of high quality injector cleaner to the fuel tank.
I do the throttle body and injector clean at least every 15,000 miles and the intake manifold cleaning about every 30,000 miles. It ALWAYS makes a very noticable difference in how the car runs.
This might solve your problem and really should be done as maintenance anyway.
