soup up, supe up

'Soup up' is correct. To soup up an automobile engine is to increase the horsepower of the engine by fiddling with the air/fuel mixture. Use of this phrase is turned into a metaphor when adopted for different contexts. Metallica souped up its concerts by using more pyrotechnic explosions. In such cases, it means 'to increase the energy of' or 'to increase the excitement of.' I often made the mistake of using 'supe up' because I believed its derivation was from the noun 'super.' I was wrong.