ive got the turbosmart tee,and having it wound up makes the boost come on ridiculasly hard,which is the way I like it,having said that my car has been tuned that way!also the boost has a very flat curve,having ran the times I have on pump and factory turbo and in a ute it has definatly worked for me,but all tuners inc mine will recommend you using the factory comp which has been proven to work! Cheers lee