um, I forgot the link but there is a really good site that explains vtec of all sorts
basically vtec-e closes one of the intake valve at lower rpm's (under 2k or 2.5k I think) so that the air entering has more of a swirling effect and mixes better with the fuel so that it can burn leaner at low rpm thus giving you better gas mileage
can get up to like 45 to the gallon or so
and is still more powerful than the non vtec sohc engines
sleeper... 16.5 mpg? wholy crap that is really bad, like far lower than it should be
the worst mileage I have ever got on my jdm b16 (stock) is 25
if you are only getting 16 you should get your engine checked