I pushed down on the rear end of my sons 97 GTP and it makes a whooshing/sucking sound. It has KYB struts but we do not know how old they are. do any GP's come with rear air shocks or load leveling suspension? the car rides like crap and I wonder how much of the ride "feel" is from the rear shocks? You would think the front struts have the largest impact of ride quality.

None come with air shocks. Don't know of any av.

How many miles on you car?

99K miles. I did look under the car and see that it has strut assy's. I have been real busy lately and have had no time to dig into anything.

Yep you need new struts. More then likely all the way around. People don't realize that struts only last about 30k miles. And yes you'll still feel a crumy ride with new struts on front and worn ones on the rear.