I've taken mine in more than enough time to lemon law it (but they always put "Dealer Cannot replocate" even when they've told me they hear it), but the last time they finally got to it and say it's my bushing on top of my left rear shock. Now they're not sure if they can fix it (the OEM bushing!!) because of the Nismo shocks! Assholes.... I'm still waiting to hear back from them and see if they will or won't, but they don't, I'm going to rip them one with NNA and on their eval...
P.S. I've had the noise longer than I've had the nismo stuff on, and proved that to them but they don't seem to care.