I'll admit, you have me stumped. And I thought I knew my Tamiya models well.
But, here's what I do know:
a. The car's mid- or rear-engined. I can tell by the chassis.
b. 10 to 1 it's a Ferrari. The engine is red, it looks like a V12 and, well, you bought it.
So maybe I don't know my Ferraris as well as I know my models, and I just don't know that car is a concept.
BTW, the only "concept car" I can find by Tamiya is a brand new one, not out yet, I think...
Take a peek. (no pix yet. )