I have an e99 and im not sure which direction to go with it. The only thing done to it right now is CAI, built trans and billet convertor, and the obvious gauges. The other thing i am planning on doing to it is an exhaust and some sort of chip like a TW or something. The question i have is, with these mods and a chip will i be better off just straight piping the stock exhaust or buying a 4" turbo back. Is spending the extra $$$ for the 4" worth the gains. I am down for either way, just dont want to kill the truck with too much exhaust. Thanks for all of the help.