Turbo's

[Jeff240sx]

The main problem with a huge exhaust side like that (look in SCC mag's "Suck, Squish, Bang, Boom" series) is that ".82 ar housings are much too large for street 4 cylinder engines, and should only be used 'race only'."
Aside from that, the usable rpm range on the KA with stock head and cams is only to 6000 rpm.  If that.  It begins to choke a little earlier than that.  You are looking at 1700rpms of power based on full spool at 4k rpm.  
Also, when someone mentioned that the exhaust pulses should be right to power that turbo, there is much more that you have to look at.  More lag based on the manifold you run, the length and diameter of the IC piping, and the size of the IC itself, along with the boost leak across the IC.  These all are factors that add to lag.  Then, you also will have less compression in the cylinders to power that turbo, which will increase lag a little more, meanwhile you will get smoked by a stock 240 based on off-boost compression.
I have a .84 housing on my shelf in my closet right now, but I highly doubt I will ever put it on.  I'm not trying to knock anyone or their research, and if you have found different information on this, let me know, but IMO, that housing is huge.
-Jeff