ralph, there are a bunch of people that make 4" kits for mafless cars, that are similar to mark h's until where the maf would be, but they stay 4" all the way to the turbo, one solid piece. I know mease makes them, but I also know you won't buy his stuff. There are others besides him, just takes some digging.
As an aside, an article in GMHTP tested a stock location intercooler vs the stocker on a few different days and ambient temperature was different on those days by 10 degrees F. The output temperature of the turbo only shifted by 2 degrees, so it seems to me decreasing the restriction is more important to system flow than lowering temperature input to the turbo. Clear as mud?
Mark:
the 12" filter would hang down too low, but how about using a 9" cylinder instead of a cone? I think there's room for it and it hangs down the same ammount. I'm not sure how much surface area you gain since my feeble mind can't figure out an easy way to calculate the cone's surface area.