So, I read in a few places that the shim is already installed on the HPS pads, and there was definately a metal plate on there.

Is that "the" shim, or do I need to go buy 4 shims?

I included the parts diagram below. It seems like part 9 is already on the pad, I just need part 8? Is it REALLY necessary? I know, silly question, but Im a nooooob at brakes.

 

The Hawk HPS pads now come with Hawk shims installed on them so it's not necessary to use any of the Nissan shims. But if it makes you feel better to use the factory stuff then you will have to order the shim set which includes 8, 9, 14, and another shim not shown in your picture. The front shim kit costs around $34 and the rear around $36 from the dealer.

 

Yea no thanks but thanks thank you very much thanks

 

NONO......... what he is talking about is the Shim set from RB.
I am still trying to find more info on that coz there is only a set of shims for the front and it costs $65. I am struggling to decide between buying the shims or go with another set of pads coz the HPS is just too noisy.

 

Oem shims are tuned as acoustic insulators for oem pads and they also function to limit heat transfer from backing plates to the caliper piston.