Actually, the 06 IX has a new turbo that none of us have ever seen or used, so no one knows yet. The one you have is superior to the previous ones, and we are all jealous. It really concerns me when newbies ask what the max boost is that they can run without frying the turbo, because I don't know why you'd even be thinking about that yet. It especially concerns me when you don't even know why the boost tapers or how to keep it from tapering. The device that eliminates the taper is the same one that allows you to turn it up to its max. This device is called a boost controller. You can use a manual boost controller (MBC), an electronic boost controller (EBC), or rely on a boost-controlling flash. The MBC and EBC give you direct control over the boost, whereas a boost-controlling flash sets it for you and provides no method for changing it other than a reflash (or installation of an MBC/EBC).
As I said, we don't know much about your turbo yet, because it's so new, but so far it's performing far beyond the previous year turbos. On my 05, for example, you can run 21-22psi daily on 93oct without worry, but the limitation here is octane, not the turbo. On race gas or alcohol injection, you can run upwards of 28psi without damaging the engine, although the turbo's life will be shorter. The 03-05 turbos are not efficient beyond 25psi, so I usually recommend 24-25psi on race gas or alky. I personally use race gas at the track, so that's when I crank up the boost to 24-25psi and re-tune with my SAFC. I would ASSUME that your turbo is capable of this, and MAYBE MORE. Only time will tell, but I don't think you're anywhere near worrying about utilizing the IX's max boost.
As for the taper, that's a built-in boost taper that is controlled by the boost control solenoid (BCS). When you install an MBC/EBC, they bypass the BCS and control boost themselves. There is still taper on the top end due to the turbo's inefficencies, but it's not anywhere as bad as the ECU-controlled taper, which is more drastic and early. Boost-controlling flashes retain use of the BCS, but they electronically eliminate the taper and give you solid boost all the way to redline.
As I said, we don't know much about your turbo yet, because it's so new, but so far it's performing far beyond the previous year turbos. On my 05, for example, you can run 21-22psi daily on 93oct without worry, but the limitation here is octane, not the turbo. On race gas or alcohol injection, you can run upwards of 28psi without damaging the engine, although the turbo's life will be shorter. The 03-05 turbos are not efficient beyond 25psi, so I usually recommend 24-25psi on race gas or alky. I personally use race gas at the track, so that's when I crank up the boost to 24-25psi and re-tune with my SAFC. I would ASSUME that your turbo is capable of this, and MAYBE MORE. Only time will tell, but I don't think you're anywhere near worrying about utilizing the IX's max boost.
As for the taper, that's a built-in boost taper that is controlled by the boost control solenoid (BCS). When you install an MBC/EBC, they bypass the BCS and control boost themselves. There is still taper on the top end due to the turbo's inefficencies, but it's not anywhere as bad as the ECU-controlled taper, which is more drastic and early. Boost-controlling flashes retain use of the BCS, but they electronically eliminate the taper and give you solid boost all the way to redline.
