Flash gt

I just purchased a 2001 GT and the car is straight pipped. It has headers which go into an H pipe with flow masters on the back. The car was located 140 miles from my house of which 135 was interstate. Once I got on the interstate was doing 70 mph the whole trip. Any time I would accelerate there was a high almost moaning whistle coming from the exhaust. It would go away when I let off the throttle but would return as soon as I would accelerate. It was so high pitched I put my finger in my left ear several times just to get some relief from the sound. I am almost positive the noise was coming from the exhaust because of how it was only present while accelerating. It was coming from the left rear of the car. I was in the car by myself so do not know if the noise was present on the right side also. Wondering if this is a normal sound for straight pipes at 70 mph or not.

Coosawjack

Maybe??