I was looking through this magazine my grampa gets, an automotive mag. There was this device you hook up to something in your car (ecu? I donno) and its supposed to test the HP and torq and what not, it was like 300$. The magazine was completely legit with real, high quality products, but i was just wondering why people dont use this more?

 

I think you are referring to the Gtech or something similar to that. Do a search in the gen auto forum for people's opinions. This will probably get moved there anyway.