My car is in the shop and they are repairing sensors etc that are under warenty but they say it is all caused by me putting cheap gas in the car Can bad gas ruin your fuel injection system?

Yes, gas has impurities in it that can cause residual buildup in your engine and cause all sorts of problems. Cheap gas is less refined meaning it has more impurities, more expensive fuel is better refined meaning more of these impurities are removed.