I have this 03 3.0 flex fuel tthat as of larely(2 months) has devoloped a whistle when throttle is pressed half way or more.... not sure what or where its coming from...please help

 

Whistles like you describe are almost always related to the air intake system. Is yours stock? Check to see if the filter needs replaced and that the hose clamps and connections are tight.

 

The IAC is known to whoooo, especially if the AC is on. So raise the hood & have a helper run the rpm up to where your hearing the noise & have a under hood listen & see if you can determine exactly where its coming from.