Yeah, if its doing it all the time I am with moutainrunner. Either you have them set too stiff, or the shocks are dead therefore not controlling the rebound like they should, or being a Jap spec coilover the springs could be way too heavy. I have Apexi T-max coilovers on my GTR and have changed the springs for something more reasonable and had them revalved. Now the car is very settled, even over bumpy roads, and with a couple of clicks to a harder setting does pretty good on the track too.