i've been pointed out to c-speeds website for this install,

however i wonder what exactly is the substance they use to seal the backing plate for the harness? it looks black... where can i get it? I cant figure what to use. I assume some sort of liquid silicon will be fine...?

 

I used Wurth Seam Sealer, pretty much any seam sealer will do the trick tho (D used some that was grey, from like pepboys or something). It's autobody repair stuff, does the trick nicely. I'd post a pic of mine, but our site is down for a bit.