If your car is 1996 and onward it has to be 100% compliant. What this means varies slightly from manufacturer to manufacturer. But for the most part, you can plug in any OBD2 hardware box into the port and it would be fine. What I find non-compliant and buggy is often the free OBD2 implementations on the web. Shoot, even the ones that you PAY for suck ass.

Calvin