Flash gt

Sorry to stir an old thread but I am having a whining noise from the rear end in my car. I see where pinion angle was mentioned as a possible cause on cars that have been lowered. The previous owner of my car lowered it what he said was a 1/2 " but I think its more like 1-1/2 ". My car makes a pretty loud whining noise only while accelerating. The noise goes away if I lift off the accelerator but returns immediately when accelerating. The faster the car goes the louder the whine gets and is mainly present in 3rd,4th & 5th gears. How can I tell if this noise is from the pinion angle and what can be done to correct the issue? Car is a 2001 GT manual.