Assuming one could get one into the states, I wonder if this would work on our VK45DE's:
IMPUL Power Throttle Valve for VK45DE:

IMPUL EXTRA POWER KIT
The EXTRA POWER KIT generates more power and produces unparalleled responsiveness. The device consists of IMPUL Hi Power Control Unit and big throttle valves. It provides the performance boost of IMPUL Hi Power Control Unit while allowing you to use regular gasoline. Needless to say, using premium gasoline for EXTRA POWER KIT can bring out more power. If a car has already been equipped with IMPUL Hi Power Control Unit, you can still boost the performance by adding the throttle valves.
Contents:
- IMPUL POWER THROTTLE VALVE(S)
- IMPUL HI POWER CONTROL UNIT designed for EXTRA POWER KIT
Also, to bring up the IMPUL 5.1L engine again...


[SIZE=-1]IMPUL Power [/SIZE][SIZE=-1]5.1 Complete Engine[/SIZE]
[SIZE=-1][Engine Spec/Tuning][/SIZE]
[SIZE=-1]Max power[/SIZE] [SIZE=-1]333ps/6400rpm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]380ps[/SIZE][SIZE=-1]/5600rpm[/SIZE]
[SIZE=-1]Max Torque[/SIZE] [SIZE=-1]46kgm/4000rpm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]53kgm[/SIZE][SIZE=-1]/2850rpm[/SIZE]
[SIZE=-1]Engine size[/SIZE] [SIZE=-1]4494cc[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]5064cc[/SIZE]
[SIZE=-1]Bore[/SIZE] [SIZE=-1]93mm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]96mm[/SIZE]
[SIZE=-1]Stroke[/SIZE] [SIZE=-1]82.7mm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]87.5mm[/SIZE]
[SIZE=-1]IMPUL Original Crankshaft[/SIZE]
[SIZE=-1]IMPUL Original Forging piston[/SIZE]
[SIZE=-1]Compression ratio up[/SIZE]
[SIZE=-1]Price : 2,000,000 yen[/SIZE][SIZE=-2] (Tax excluded)[/SIZE]
[SIZE=-1]Note: Installation cost is not included.[/SIZE]
http://www.impul.co.jp/
IMPUL Power Throttle Valve for VK45DE:

IMPUL EXTRA POWER KIT
The EXTRA POWER KIT generates more power and produces unparalleled responsiveness. The device consists of IMPUL Hi Power Control Unit and big throttle valves. It provides the performance boost of IMPUL Hi Power Control Unit while allowing you to use regular gasoline. Needless to say, using premium gasoline for EXTRA POWER KIT can bring out more power. If a car has already been equipped with IMPUL Hi Power Control Unit, you can still boost the performance by adding the throttle valves.
Contents:
- IMPUL POWER THROTTLE VALVE(S)
- IMPUL HI POWER CONTROL UNIT designed for EXTRA POWER KIT
Also, to bring up the IMPUL 5.1L engine again...


[SIZE=-1]IMPUL Power [/SIZE][SIZE=-1]5.1 Complete Engine[/SIZE]
[SIZE=-1][Engine Spec/Tuning][/SIZE]
[SIZE=-1]Max power[/SIZE] [SIZE=-1]333ps/6400rpm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]380ps[/SIZE][SIZE=-1]/5600rpm[/SIZE]
[SIZE=-1]Max Torque[/SIZE] [SIZE=-1]46kgm/4000rpm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]53kgm[/SIZE][SIZE=-1]/2850rpm[/SIZE]
[SIZE=-1]Engine size[/SIZE] [SIZE=-1]4494cc[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]5064cc[/SIZE]
[SIZE=-1]Bore[/SIZE] [SIZE=-1]93mm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]96mm[/SIZE]
[SIZE=-1]Stroke[/SIZE] [SIZE=-1]82.7mm[/SIZE] [SIZE=-1]>>>[/SIZE] [SIZE=-1]87.5mm[/SIZE]
[SIZE=-1]IMPUL Original Crankshaft[/SIZE]
[SIZE=-1]IMPUL Original Forging piston[/SIZE]
[SIZE=-1]Compression ratio up[/SIZE]
[SIZE=-1]Price : 2,000,000 yen[/SIZE][SIZE=-2] (Tax excluded)[/SIZE]
[SIZE=-1]Note: Installation cost is not included.[/SIZE]
http://www.impul.co.jp/