i have a 02 gt basically stock, it ran fine until saturday night. now it feels sluggish and when i hit the gas it whistles like i have a turbo. it is not throwing cels
you can also check the IAC valve, mine was making loud noises on the 'stang as well as on my 98 Lincoln. You can soak /clean them in gumout, but it only buys you about 3-4 months until the drone is back.