Why doesn't the A/C in my car blow Air fast enough like it should?

I have a 2005 Ford Mustang V6 & for some reason it won't blow air fast enough like I think it should I put it on maximum A/C on speed number 4 & I can barely feel the air any ideas?

1. Have you ever replaced the cabin air filter? What is that? You said
I bet is clogged up

2.is air coming out of any of the other vents other than the ones selected by the knob controller? Yes as in floor vents or as in windshield (defrost position)
there's a vacuum leak at some place between the intake and the climate controller.

It could be caused by a bad blower speed selector switch, blower, blower resistor, wire, or wire connection, this wiring diagram will help to diagnose for the cause:
http://iihs.net/fsm/?dir=40&viewfile=Manual%20Climate%20Control%20System.pdf
Save the link for future repair (Wiring diagrams for the car)
E mail if you need more help. Happy hunting. HTH

Edit: You can buy a multi-meter at your local auto part store to diagnose the problem. They're cheap now a day.

Are you sure the blower motor is truly spinning at full speed eventhough you've got the fan on high? A bad blower motor resistor is normally the cause for this.In otherwords, you have the fan on high but airflow is barely coming out.Another thing that causes little to no airflow is when the evaporater core ices over.Anytime the ac is on max the fan has to be set on high also. If the fan is set to a slower speed or the fan is malfunctioning spinning at a slower speed, it will cause the evap core to freeze up. When the core freezes up, warm air and little to no airflow will come out of the vents. If this occurs, turn the temp setting to its warmest level with fan on high and it will take 10-15 minutes to de-ice. Try turning on the heat to see if only a little bit of airflow still comes out. If airflow barely comes out, the blower motor resistor or blower motor is malfunctioning. Make sure the condenser(in front of radiator)fins are clear from leaves and debris.

AC is designed to cool a space, and it doesn't always need a strong airflow to do that.

Um the car is almost a decade old.

Maybe it done need fixed