Boost leak after rebuild

[4rsfed]

Hello,
I just completely rebuilt my engine about a month ago and I when I punch it out it pulls until about 4500 rpm it cuts out and then it looses all power. It starts to sputter and sounds like a machine gun when it cuts out. There is also a lot of black smoke out the back when it cuts out. If I don't go WOT and slowly work my way up it will not cut out and it will go to redline. I replaced the plugs and wires and it did not help the situation. So I did a boost leak test and the only place I can hear a leak is at the turbine housing. I'm wondering what could be leaking there and how you would fix the leak. Is there another possible cause for the sputtering? or would that leak be the problem?
My car is a 92 Talon and it is completely stock.
Thanks for the replies.

 

[dnhieu]

is your mass air flow sensor connected

 

[hereitcomes]

is your mass air flow sensor connected

if the MAF wasnt connected he couldnt even get out of first. let alone 4500 rpm. they dont like running at all without that damn sensor.

 

[4rsfed]

Yes the MAF is connected.