I have an annoying pop on the left front suspension under moderate bumps in the road, I'm thinking its the FRPP/GT500 top plate, but here's what I've checked:

Put car in air, check for play in tire at 12/6, 3/9 positions
checked torque on strut retaining nut
checked for play in swaybar endlinks and brackets (do need to regrease bushings)
Visually inspected all components (though admittedly, I didn't look at the LCA bushings very closely).
Checked and adjusted brake duct interferences

Its not on the right side, and testing over rough roads definitely pins it on the left. I guess its time to get some CC plates, but was curious if there's anything else I need to check?

 

Had the same problem a few days after I installed the lowering springs and the Koni's. I made sure all upper mounting nuts were tight which they were. I took the car to my local mechanic and he didn't find anything wrong with the installation. He then took the air gun and hit all of the upper mounting nuts again just in case. Didn't see the air gun move at all (meaning all of the nuts were tighten already) but yet it fixed the problem Probably you should do the same.