Just bought my 2008 Mustang GT/CS and the previous owner has Eibach Springs with Caster Camber plates installed and every time I hit a bump I hear a knock coming from the driver side front wheel. I work at a dealership and me among other mechanics checked the sway bar link ball joints and tie rods and could not find anything wrong, loose, or worn out. I owned a 05 mustang before this that did the same thing, just not as bad. Any tips/help is appreciated.

 

What caster/camber plates are in it?

 

Depending on which brand caster camber plates they are and how long he's been driving on them, that very well could be it. Usually noise will be heard when steering left to right from the strut mounts though. Also check the fender wells if you haven't already for rattles.

 

Common issues on these cars for front end noise:
Control Arms (ball joints)
Stabilizer links
Strut Tower mounts - Just saw you have caster/camber plates so this doesn't pertain to you but it could still be an issue.

All three have TSB's out for them for OEM parts. I've replaced two of them (Tower Mounts and stabilizer links) this past weekend. 2010+ have a redesigned stabilizer link that makes it easier to torque to spec and once torqued is less likely to come loose. (better lock nut and fine thread along with a nut at the base of the stem instead of just the 8mm end.)

Most of the knocking is gone now but I still have some and the ball joints are shot to shiz so that's next on my list. I already have them (FRPP control arms) but I was too tired to replace those along with the rest of the stuff all at once.