I don't have either one, but I read a lot about both of them. I honestly haven't heard too many good things about the Stillen SC. People have a lot of problems with them, the tune they give you is absolute crap, and they don't make much power. Stillen's product quality and customer service have started lacking severely for the 370Z, whereas GTM has done nothing but improve and continue to please people. If I were to consider a SC I would be looking at GTM before anything else. Just my
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