i work and own some all jdm cars,if you know what youre doing you can keep the ac heater,ps and everything on and still get 500 hp out,but if you take it to someone who doesnt know what they are doing you might end up with out ac,and ps..wiht out the ps,ac,heater and other pulleys you get a little more power,but i'll go for a t3 kit,they work amazing,and get a turbo timer,and boost controller...it gives you more