Test flew a Cherokee 140 with the 160hp upgrade. 30ish hours on a 2013 OH (yes I know...) Engine ran smooth, started first crank after admittedly sitting for awhile, nice little trip around the pattern and town with the only squwaks being a push to talk that seemed sticky and a oil temperature gauge that never came up. Seemed to pull a little right on taxi/takeoff but the right seat guy (me) weighed a good chunk more than left seat guy, and right tank was also full vs tabs only on the left so I thought it was that imbalance. However after we landed and got it back to the ramp it was VERY tail low. Nose gear strut was stuck fully extended. After we disembarked and did some yanking the nose strut eventually gave in and went to a normal compression, and then I noticed the right main strut also sat slightly too low compared to left (and by now that fuel imbalance should have been negligible). Owner/seller of course trying to play it off as an overfilled front strut and underfilled right main strut. Is this actually a case of struts going bad from sitting too long and needing rebuilt? If so, anyone know a ballpark cost for that?