okay i just did a swap with my friend because his d15z1 droped a valved and its fried .... so we did a d15b7 beacuse it had a about 10 more horses but its running real shitty when u hold the rpms at like 3 grand and lit it sit there at that rpm it sounds like its htting a rev limiter and back fires a little. sounds like its misssing but its not. holds idel, and when u floor it it sounds good and dose not choke or anything... i know the d15z1 had a five wire o2 sensor . and this one has a four wire but its not installed due to the dc header not having a whole were this motor had it should we wire it so it goes behind the motor by the cat???? also we are running a p05 ecu/..