'03 Civic EX, 210k miles, owner for one year.

Getting codes:
P1259 VTEC System Malfunction

P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected

Basically whenever I am driving down a slight hill, sometimes on a flat surface, and just maintaining speed the CEL will flash. The car doesn't actually seem to drive any different while it is flashing, and it stops flashing if I slow down a lot, or sometimes stops quickly on its own. I can prevent it by shifting into neutral, or by accelerating more, but neither seems like the best long-term solution to me.

I've gone through probable causes of the P1259 code and replaced the VTEC pressureswitch, cleaned the VTEC solenoidvalve screen, changed the oil, and done one drain/fill of ATF, but the problem persists.

Halp?