what is BEST way to increase power on an 2014 Terrain SLT?

Make sure any modifications you do are GM approved parts or you will void your factory warranty. Are you trying to soup up a 4 or 6 cyl.?

I have a 4 banger in my 2014 Terrain. Around S. Ca. I feel there is enough power except trying to pass or merge onto a fast moving freeway. On my road trip, passing took me back to the 50 and 60s cars for passing power. IF GMC would come out with a 4 cylinder turbo diesel, I'd be the fist one down to trade in my new Terrain for one. My daughter has a six cylinder MBZ C350. When I took it in foe service, I drove a new MBZ C230 four cylinder turbo. Way more power than the six. So if power is what your looking for, check out turbo power. A blower will cost a ton of money, void your warranty and blow your engine as it is not made for that. The cold air intake is not all that good as tested by Road and Track magazine. The manufactures that sell them will tell you different, but the dyno does not lie. I believe the six cylinder is around 80 more HP but 30% less mileage.

i have a terrain 2015 whats the best way to install a chip or super charge on it ?

Go online for chips for the Terrain. There are also instructions on how to switch out the computer chips and program them. BTW, GMC di come out with turbo powered Terrains, a small CC 4 banger a larger CC 4 banger and a 4 banger turbo diesel. We'll have to see what the price change is and HP/economy.