DS8 didn't talk for conversation purposes until after he was 2, but he was reading by then, and he knew all the numbers anybody could ever want as well (he loved Who Wants to be a Millionaire and knew all the $ amounts, knew when something was money or just decimals, fractions and all that). We knew from 1 to 1 1/2 that he was very gifted, but it wasn't until he was 6 that he was diagnosed with Asperger's. We had suspicions from 4ish, but resisted it.
He did some of what I guess is echolalia, at least he would repeat things back to you, whole sentences usually (really interesting because he could repeat a sentence back without the words that he wasn't allowed to use). He had a ferocious temper, and would bang his head on things (floor, couch, walls) when things weren't going his way -- he still has a temper, but he's learning to handle it in more positive ways. Back then, it was easy to see that it was just because of the things he wanted to do but was not physically capable of doing yet, now it's frustration over being misunderstood by the other kids.
So basically, you're close to where we were six years ago! I would not hesitate to say your DS is gifted, and therefore frustrated, and it wouldn't surprise me if there was some degree of Asperger's as well. Or some of those other things. You're in the right place, here!
Don't be surprised if he gets interested in license plates -- they are numbers at a handy height for a 2.5 year old.
