Ok it will not void your warranty, because the dealer has to prove what you put on your car messed up the car. For example, If I put an exhaust on my car, and my radio stops working the exhaust that I put on is not going to void the warranty on the radio.
About Greddy, on back order for 6 months, that is the truth, Greddy is not a place you want to order anything from. If another after market place carries Greddy then I would get the product from them. Greddy takes to long.