the overall suspension design is pretty similar, but the RSX-S gets stiffer springs, 19mm rear sway bar, and a few tie bars - front and rear. The wheels/tires are a bit better too. The skidpad numbers for the RSX-S are slightly higher than the EP, but not a whole lot. I'll tell you that if you get a set of lowering springs, swap in the RSX-S rear sway, a couple tie bars and some decent rubber the EP can be made to handle a lot better than the RSX-S.
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