I think Rennetech was first to do the 178 set, because they were like the only MB tuners at the time. Then other companies copied the 178 pulley. I think it is pretty good that LET came up with something different, in fact if it wasn't for LET what would you guy's all fight about. When we do the ATCO track in NJ, I will be bringing my car with the 181 set up and SL-55 intake and we will see how well the combo performs. It is kind of like Goldilocks and the three bears, 178 tooo small 185 toooo big, 181 JUST RIGHT