After doing some research you really don't need to upgrade the Shelby coils unless you're making 1000plus hp(I'm assuming this to be at the crank).Stock coils have a hard time keeping up when a lot of boost and pwr come into play.One example I was given was a customer's '03 cobra running 8's with 750rwhp and w/weaponx coils he picked up 50 more rwhp.To the best of my knowledge,Lethal`s 9 second Shelby still only runs the stock coils.