Cant find Suspension noise

2004 Nissan maxima
 


I can't find where's the noise coming from when car is off the ground.  I took it to Goodyear/sear auto center and they keep saying that my car is stiff so that can't figure out where's coming from. Once the car is on the ground then go for ride later same noise is still there.

Then how can we find the noise if car is stiff? 

The issues I have is I hear thumping noise in the front at low speed when going straight or turning either way and on the rear I hear popping noise when turning. I wonder if my coilover is blown? Rear end is boucny when I hit bump on the hwy, but no noise at high speed only at low speed.

Mods I have is;
 
D2 racing coilover had them 2 years
Front/Rear Red lion racing subframe bbushing, front lower control arm bushing change to red lion bushing, front new axle,
 I had rear red lion lower/upper control change but I thought I had noise coming from there so I put rear lower/upper back to oem, racingline rear endlink, and nismo front/rear sway bar.