yup... the same thing happened to me when i installed the AEM CAI. before my idle was at around 7-800 and now it is at 4-500. sometimes after reving hard and stop at signal lights... i see it idle at around 2-300. i think it should be normal... as long as ur engine doesn't start to choke. occasionally on hot days.. i did noticed that sometimes my engine is about to stall and i have to rev it just to wake it up. go figures~?