its been covered a bit. but anyway, as for 400 hp, theres a few things we need to know.
is your car a turbo or N/A? if its turbo, simple upgrades can get you close. if its N/A, good luck with 400 hp. is it auto or manual? autos suck up more power than manual transmissions, so plan on it being harder to get 400 hp from an auto. next, what do you use the car for? DD, racing, mix? build it for what you use it for most, or u will hate driving the car.
turbo models u should look into a basically full rebuild for the engine. head, block, etc. balancing the rotating assembly will help. then a turbo upgrade (drift motion i think sells some good upgrades, or have your stock one rebuilt) would be a decent way to get some more power, as well as a FMIC kit, some 550cc injectors and a lexus AFM mod. probably upgrade the fuel pump while your at it, just to be sure. a walbro 255lph pump is a good unit.
having everything done right is the best way to ensure good power, so for the machine work, a reputable shop that is familiar with these motors is a must. as for assembling the block, check, re-check and then check it again. as long as your careful and follow the directions and measurements in the manual, it should go fine.
anyway, hit back with more info and we can advise accordingly
