I know your operation, and know you guys run a tight ship. I am in Columbus, NE and grew up between Columbus and Grand Island.
This is what I see with Car Gurus. When my inventory gets twisted up and ages, we drop prices. As we drop prices, our SRP>VDP>Leads go way up. The down side of this is of course that Gross Profit goes way down as Car Gurus leads go up. I don't have the ability to systematically analyze this. I simply have to look at each lead individually. Generally speaking, my fresh inventory leads (units with Gross in them) on Car Gurus are more commonly non responsive leads.
So, yes I do get inventory views and leads from Car Gurus. Unfortunately they aren't typically leads that convert to much Gross Profit. But hey, they are better than a loss at the auction!
Cars on the other hand hasn't proven to be a good Lead source. There is certainly more to it than Lead count alone. My SRP to VDP percentage runs about 1.25% on Cars. Car Gurus runs about 4%.
I do not see the reverse correlation between the two like you do. You hate to write it off as coincidence because you have such a large pool of data supporting something otherwise. Interesting to me.