My final mod in my quest to 500HP was a bigger TB.  
Unlike a turbo, all the air that enters the motor must pass
the TB under standard atmospheric conditions.  
Therefore, for the same level of power the blower TB
must be larger.  In my case, measurements of vacuum
between the TB and blower showed about 2" of HG at
full throttle indicating that the 75mm TB was too small.  
So I went big, probably too big at 90mm.  
I didn't  want to deal with another
complicated sheetmetal manifold
so I designed this interface plate
which allowed a much simpler
manifold as shown in the
accompany picture
Here's a few pictures of what the
TB sees
Just a bit of difference. . . . . . . .
Here's the almost completed
manifold with 90mm TB installed.  
I've yet to weld in the connection to
the bypass valve (blue hose).
As you can see, I needed to move
the overflow bottle down a bit to
make room for the airbox tube
On my first "test run" the motor
managed about 12psi but
unfortunately this was a bit too
much for the stock pistons.  Here's
the data log for the pull that did my
motor in.  Nothing particularly
alarming (note, the O2 #2 sensor
always shows about 1/2 point too
lean).
This is what happens when the ring
lands let loose.  All but one piston
suffered the same fate.  So now it's
time for a rebuild.  See section
"Engine" under Rebuild for the
details.