I was going to pick up one sti radiator cap, the 1.3 bar one, but I wanted to see what everyone thought of the efficacy of this mod at actually making the cooling system more efficient. Saw one thread on a radiator exploding but not clear if it was the caps fault or not. So, do you have to buy one or two? Is it a good mod to make the cooling system more efficient? and Can it be dangerous on a stock radiator?