I have not personally used one.
But from the looks of it & design,I would have to say it will increase fuel mileage,even w/a mild cam upgrade from stock,should do nicely.
The intake port velosity should increase,therefore giving you more low end torgue.
I have witnesed (SP) & drove first hand,a SP2P intake on a mild SBC 350,,,let me tell you,it had all kinds of bottom end torque,but it also had no top end power,not even close to the top end a SBC Perfomer intake.
On the SBC SP2P intake the RPM range is very low.
Here is one now for sale.
http://cgi.ebay.com/ebaymotors/HOT-ROD-E...181310005r35387MBHD