Figured it out. It is an aftermarket shock of unknown brand. I'll take it out this weekend and either add a heavier spring or replace it completely.
Thank you. Very good point. I weigh 230 lbs and the rear shock is nearly at it's preload limit. The front is a little soft not terrible but I understand your point about the relationship of the two. I'll address both.But if you put on a stiffer spring in the rear end, you just have to replace the front fork springs too, or the nose dive will be too much.