Puzzled1, puzzled no longer...
The VTM-4 essentially operates in three modes (same for 2002 as 2001), they are:
1) Torque is sent to the rear wheels proactively whenever you accelerate - called acceleration torque control mode (ATC) - this diminishes the possibility of front wheel slippage.
2) Whenever slippage (spinning wheel) of one of the front wheels is detected by sensors, torque is sent to the rear wheels to enhance traction.
3) Engaging the "VTM-4 lock" switch. This is used when the vehicle is stopped and stuck. The transmission must be in 1 st, 2nd or in reverse for this mode of operation to engage when you depress the "VTM-4 lock" button. The rear axle becomes "locked" so torque is sent to the rear wheels (in addition to the front wheels) up to a speed of 18 mph. If you exceed 18 mph this mode of operation automatically disengages until you reduce your speed to below 18 mph. As you increase your speed above 6 mph up to 18 mph (in this mode) the ratio of front/rear torque gradually increases. This mode of operation may only be used on slippery or loose surfaces.
Please note that under normal operation ("VTM-4 lock" switch off) the VTM-4 is not a "full time 4-WD" system. Once you achieve a constant speed, torque is only sent to the front wheels when you drive down the street or highway. This improves gas mileage.
Regarding a new engine with more horsepower for 2003, I've seen that reported in the media (AutoNews), but this has not been confirmed by Acura. Until they do, it's nothing more than a rumor.