chipping CPU will void the factory warranty, so be careful on that. GT3 bumper is cool as long as the paint job is done by qualified shop. I have seen after market bumper/spoiler's paint start chipping, and that my friend will definitely hurt the resale

 

I have been doing mods on cars for more than 25 years, and my experience has been that mods translate into less value when you sell, but more enjoyment when you own. Since I am now having a supercharger put in my 997S cab, you can say enjoyment means more to me.