Are there model markings on the trunk?
It only has the A caliper symbol (no more ACURA lettering), the TLX badge, and the SH-AWD (if you have that model). Otherwise the only way to tell I4 from V6 is the wheels.
I think that's where Acura dropped the ball. They could've made some slight variations on the bumpers between the two, but it pretty much all comes down to wheels and if you can peek inside, the shifter.

