I would suggest using a higher ( letter wise ) turbine trim & use a smaller A/R turbine housing if you want it to be streetable & still boost at a lower RPM.

This will allow for the exhuast to still breath & not be so restrictive because of useing a smaller trim wheel.

This is what I did on my Syclone w/great results.
http://en.wikipedia.org/wiki/GMC_Syclone

It makes 386 HP @ 4000 RPM & 550 ft lbs of torque @ 3000.
It makes more now w/a larger compressor wheel I machined & installed.

My torque converter brake stalls to 2100 RPM max & can reach full boost (if I want to) right on the launch.

Back to straight six stuff:

I used for many years ( at least 12 yrs ) as my daily driver a non heated intake manifold/s.

I got as high as 21 mpg,never bogged or puddled fuel in the manifold,as I stated earlier the intake gets hot,it is surrounded by hot headers belowing hot/heat air,thermal radiation,too much for my taste.

Again two cents thrown.

MBHD

12 port SDS EFI