Which hx40? There are a couple of them. Now there are some many better turbos, that its really only worth running an hx40 if you get one dirt cheap and aren't looking for a lot of power. It will really only support up to around 375-450hp while still staying in its map. So, a plate, some injectors, timing and AFC mods, maybe some small dv's too. Just make sure you do the supporting trans and head mods. Also make sure you get the hx40 with the 60mm comp wheel or else its not going to do you much good. Years ago, we set up an 01 with a PDR hotrod 40, and that truck put down 468 at the wheels, and ran a 13.03 with that set up. It would get extremely hot though too.
Sean