Why wont my car idle properly?

Hey, i tried to get my car smogged, but the car wont hold an constant idle between 2500-2750 rpm, that the smog machine required for the test. the car just rushed up to 3000+ rpm. I have replaced the MAF, O2 sensors, idle air valve, and EGR, to fix other issues, but the car still wonthold a steady idle...HELP