HELP: Clunk Noise after Coilover Install

HisStigness

Hey guys I really need some help, just got HKS Hipermax IV GT coilovers installed a few weeks ago that I brought brand new from CZP. Had my mechanic install them who has a lot of experience installing coilovers for various cars.

Under normal driving conditions and just normal size or small bumps, everything is fine even under cornering. But if I hit a really harsh bump or go over a sharp crest where the car first unloads and then reloads a lot on compression, I get a very loud clunk noise only from the back right corner, 100% positive that's where it's coming from, it almost sounds like metal on metal but hard to tell for sure.

This comes after I already took it back to my mechanic once and he thought the rear right might by bottoming out on the fuel tank tube that goes from the gas cap to the tank, so I stiffened the shocks up a lot more (4 clicks from full stiff front, 3 clicks from full stuff rear), it was fine for awhile after that but it made the sound again last night after a big bump on the highway. Never once did this with my stock suspension and I left the HKS's in their factory settings which was a 3/4" drop.

Really hope you guys can help.... Thanks.