Au series 2 Xr6 vct, Air leaking ?

[FTe001]

Hey All,
Friend of mine has a series 2 Au Xr6 Vct,
And when ever the car is running you can hear air leaking quite
Loudly also runs very sluggish since this air problem has started someone suggested replace the small plastic F piece under the throttle body done that and still no good its around under the throttle body area you can hear it,
Any help is greatly appreciated.