You can bolt on the RH kit and it will run as smooth as the Greddy kit. The difference really is in the installation. The Greddy kit will be ridiciulously bolt-on, while the RH kit may require you to shave the block a bit, work with the piping, etc. Nothing too ridiculous though. The only thing the RH kit IS missing is an intake, but thats a couple bends and a filter, no sweat.

I say go RH or Drag. I wouldnt bother with the Greddy kit personally unless you KNOW you wont be upgrading anything in the future, and absolutely cannot handle a mild installation yourself.