In thoery if you add a couple of psi ( more air in the cylinder) you should save gas? so would electric turbos work? i do understand they run of electricity and so it adds one more thing to be driven.
Mark,
a well discussed idea as 2000mc has mentioned.
Another way to increase the VE of an engine is by using induction and exhaust tuning.
David Vizard has written extensively on this topic and his books and articles are well worth finding.