Theres a few key signs.... one is being able to drop into 1st above 34-35 mph. Another would be fans coming on at any point below 200 degrees while running (I dont remember stock temps and i have hptuners on my other laptop). Also while our pcms all have the ability to run the fans for a bit after shutting the car down none of our cars came with it enabled so if the fans run at all after shutting the key off you know you have a tuned pcm of sorts as well. There is also the typical removal of the speed limited but unless your in mexico be careful about testing that. You could also try pulling the egr plug off of the egr and see if it throws a check engine light. Most tuned pcms remove all of the emissions checks.

Only way to really really know whats going on is to have someone dump your pcm into a laptop and check it.