I bought the z1 kit because of the 4 silicone couplers to the throttle body. Fitment wise, Ash's kit fits alot better along the radiator and the turbo outlet pipes have a lot more clearance from the bottom of the plenum. Also if you plan to run meth injection, ash's hardpipe can easily be tapped for the nozzles. I installed the planar inlet kit with the engine in but I wouldnt recommend it. It is very hard and frustrating. You will have to grind the driver side motor mount bracket. Get the selin translator with the elbows and it will save you a lot of time and headaches. I dont regret installing the planar inlet but im used to difficult installs like that.