Take out the EFI fuse to reset the ecu. Keep it off like 1 hour and put it back. Turn the car on and let it idle until warm. Otherwise it will take some time to notice the change.
I tried to order one this summer and first they told it will take 6 months to be made, but later RHD informed that it is discontinued and I got my money back.
Mostly ok, louder than stock, but nothing like Fujitsubo. If you are sitting around 3k on highway you can still hear music and talk normally with the deep BOOOOOOOO on the background Give it some and will go like BRAAAAAAAA
Stabilizer won't help with your issue, because they are designed to remove electrical noise and very small voltage spikes, not to compensate the current drain. You can buy a big audio condensator to help with the current drains or a better battery.