Long story:
basically, the 2 rings on top of the spring, they were practically as LOW as they posible could be. there was like 1 thread left. when the suspension hung loose, there was a gap between the spring and the ring. On the left side there wasn't. i took everything out of the spring assembly. turned the collars enough to get out that to the very last thread, and put everything back. so essentially i have the most preload possible, however, the spring still has a little gap when hanging loose. ii fully expected to not have fixed anything. basically it seems like theres not enough threads on the spring perch, even though i'm lowered .75 inches, it seems like my car is too high or w/e to get enough preload. so anyways, i adjusted that ring maybe HALF a turn. all finished, i expected the sound to be there and was totally surprised that it wasn't.
i honestly think the installer put as much preload as they could, i just put a miniscule amount more, literally i could not possibly pput anymore preload because of the amount of threading on the spring perch. i remember the guys at the shop even saying it was at max preload and complaining how they wanted to add more but couldn't. so i dunno, i think BC might need to modify the design . maybe the sound only presented itself because i'm not lowered that much in the rear. Mike from BC said i'm almost at max height, which doesn't seem to make sense but w/e i'm gonna talk to them tomorrow and explain. i now have this really slight creeking sound but its not all the time, maybe a loose interior panel or something... i dunno, but its not really that bothersome, nowhere nera as bad as that goddamn rumble rattle.
Short story:
It appears as though, based on my ride height (.75" lower than stock, which is not that low), and the fact that i have 210mm springs, i have to max out the preload. However, there really isn't enough threading to do so.
It is my opinion that this was neither installer error, nor was it a defective product. it was just a matter of my ride height and the maximum amount of preload that can be put on the spring based on the amount of threading and the length of the spring. The solution: BC Racing is going to send me 230mm rear springs or spring spacers, whichever i want. i am most likely going to go with the 230mm rear springs. After my little escapade last night, i feel totally comfortable swapping them.
A major rep goes to Mike and BC Racing for talking to me on the phone for god knows how long explaining everything and sending me pictures of how to make any adjustments. Also, i'd like to thank Performance Motorsport for helping out diagnose the problem. they DID do the install correctly, and these are not defective shocks. i just happen to have my ride height set pretty high in the back. that is all. after adding what miniscule amount of preload i could, the noise went away. But with the longer springs, i can move the rings way up higher and have more preload to play with.
SOO if you do get these coilovers, which i really do enjoy, and you plan to only do a mild drop, ask for 230mm rear springs. If you drop any more than .75" in the rear you should be fine with the 210mm springs
ok so that wasn't very short, but i feel much more comfortable working on suspension now