the tuner plugs in under your dash, if you take a peek, on the drivers side, youll see a plug in the shape of a trapezoid. the tuner does not STAY plugged in, you only plug it in to load a tune and then you can unplug it and put it away
You'l notice a difference. I drove Kyle(HarryTasker)'s truck stock, then he put in 92 perf (i belive) and I did notice a difference. Not huge like a supercharger, but still a very noticeable difference.