R34 GTT Mid-High range power loss

[Crossfetch]

R34 GTT Mid-High range power loss

Hey Guys,

I'm new to this whole Skyline thing. Just bought myself a R34 GTT about a week ago. Runs great.. Besides getting sub 250km a tank.. Yeah.. I also feel when it comes onto boost its fine but as soon as you go over 4500 rpm it starts to splutter a bit then comes back. While that's happening its blowing a crap load of black smoke out the back. I'm assuming it has something to do with 02 Sensor? I had a look through the receipts and I saw that it has Spitfire coil packs.. Not too sure what they are but they were $600.(I mean I know what coil packs are) Previous owner must of got a CEL because he got it diagnosed and it said bad 02 Sensor. Next question is how much and where is it located... If it's even got to do with the 02 sensor.. Im not sure.. If someone could help that would greatly be appreciated.

[Ben C34]

O2 sensors won't do that.

A Boost leak will. Amongst other things, but let's check the easy stuff first.

You have to pressure test to be sure, just looking doesn't cut it.

[Crossfetch]

Hey mate.. Yeah well first problem.. The guy that owned it put 3 Defi gauges in. Decided to wire all them up to power.. That's it. So I actually have no boost gauge.. Would be good if I knew how to get one working haha.

[Dose Pipe Sutututu]

Running stock boost?

[Crossfetch]

That is what I'm not sure about...