My idle is 550 RPMs (like the R&T guide says) w/o A/C and 750 w/ A/C.

Try fuel system cleaner, and check for leaks in your air hoses. Run the car hard while the fuel sysem cleaner is in there (and make sure your oil is within 3k miles of use (the more I read, the more I realize people are going longer than that...BAD BOYS AND GIRLS!)