Got an update on this issue, which popped up yesterday.
Volts got real low (dipped below 12 while engine was running), HICAS system goes spastic (flashing light, can very clearly hear the pump going off every second, steering obviously kicking in sync with the pump). The voltage would go as low as 6.5V while driving (lost radio, and eventually HICAS).
Went and bought a new battery, all sweet for a few minutes until the volts dropped below 12.5V.
Strange thing is, sometimes the volts would go up to the usual 13.5V mark and everything will run sweet.
So, the HICAS system is very sensitive to the voltage (as documented here on SAU), the strange thing is trying to locate source of the voltage drop.
I hope the alternator isn't dying. I've cleaned the plugs at the terminal with contact cleaner it fixed the issue for about a minute. One of the fusible links is a little dodgy, I might try to replace the terminal.
I'll also have a look at the alternator tomorrow and hopefully find some sort of resolution.
*edit*
Unplugging the HKS turbo timer doesn't make a difference. I'll suss out the wiring anyway in case it's not grounded properly.