It's not brake or suspension. I've had all those bolts out.

 

Not from your z.. Ive had every bolt off around and in the engine bay, all suspension, transmission, struts, everything that can be unscrewed ive unscrewed it basically.

 

I think I can end my concerns and close the mystery.

Thank You to all, I never would've questioned it not coming from the Z until you guys had good confidence it is not found on the Z.

It must have been a bolt I took off my buddies Tundra. As we removed two brackets with OE Toyota bolts that were replaced with the bolts that came with the hitch, As the replacement bolts were 19mm.

 

http://www.tacomaworld.com/forum/2nd...s-washers.html


that was a 30 second google search.

you have no worries now.