Without sounding patronising, your best bet is to get someone to drive it you trust, and who is used to modded cars suspension wise, as you will be able to feel what is wrong.
eg if the car was bouncy for example and got thrown around and off course a lot mid corner when hitting a bump at the front or rear the springs are likely too hard, BUT with coilovers most rear are adjustable for BOTH compression AND rebound at the same time, with just the one adjuster, whereas fronts are normally compression only.
Need more detailed info about how it drives, does one end feel a lot different stiffer/softer than the other for example ?
tabetha