Did you do the brakes or was it in a shop? if the brakes bled improperly there could have been air in the lines or damage to the brake booster. The vx is different in that it must be running and the ABS must be disabled in order to bleed the brakes properly. many people wouldn't bother to find this out before bleeding the brakes and it could have some serious consequences
Why does the engine have to be on? I did mine back in April, with the motor off, and haven't had any issues. Stops great and the pedal feel is just as good if not better than before.