VTEC-E can engage from 2500-3300 RPMS based on what I've seen for throttle input and vehicle speed. So it would be possible to stay out of VTEC-E and still be in lean burn for quite a while on the highway.
You can always throw an LED on the Spool Solenoid (negative trigger, ECU grounds the solenoid to trigger) to see when VTEC-E engages.
Here's the Factory dyno plot and BSFC for the VX:
Green is torque, blue is BSFC
It might help to calculate your HP at the given RPM Mike.