Chips increase hp by increasing the timing, boost, and modifying the fuel delivery. I think the main increase for me comes solely from the timing because my boost is regulated manually anyway. Cold start and drivability are usually improved too. If you have the money, get the Max Effort thumbwheel chip. Nothing even comes close. You can adjust you fuel, timing, and a ton of other things from inside the car and you never have to adjust fuel pressure again. To go from pump gas to race gas requires a couple tweaks from inside the car and you're done. Every aspect of it's performance is better than anything I've ever tried, especially the drivability and spoolup.