Regarding the intake manifold/inter-cooler posted above -
It would be interesting to see what that individual did internally, if anything, inside the intake to clean up the air flow. Large volume changes, like what appear to be the case there, are never a good thing in fluid flow, especially if the fluid is compressible. But the interior flow passages could be dramatically different than what appears on the outside, so to comment otherwise is purely speculation.
The intake on a 1HZ appears to be less than ideal, from an airflow perspective.

(It appears to be ideal for cost effectiveness, and ease of packaging, however) On several occasions, I've pondered building a "header like" intake for my 1HZ, but really need to install the turbo first. Then, once a top mounted inter-cooler is added (like Wayne's 1PZ), a simpler tubular manifold connecting the cooler and the head could be built.
The existing 1HZ/1HD manifold should perform relatively better under pressure, but there still must be very significant pressure drops with all of the hard/square 90's in that design. A significant reduction in pressure drop by replacing that manifold has to be available....
Just my 2cents worth......
And paraphrasing Wayne...
"Hey, I'm just an engineer, so what do I know?"

