Seems to be secret decoding....

I'll post here what I know along with how I have it mapped:

JOYX - Right stick X axis (Turn) - invert = 1
JOYY - Right stick Y axis (Pitch)
JOYZ - Left stick throttle axis (Accel) - invert = 1
JOYRX - Left stick thumbwheel around the I button (Roll)
JOYRY - Left stick thumbwheel around the E button (Throttle)
JOYRV - Right stick, center hat switch (StrafeLR)
JOYAXISA - Right stick, center hat switch (StrafeUD) - invert = 1

JOYBUTTON0 - Right stick, bottom trigger (+Shoot2)
JOYBUTTON1 - Right stick, top trigger (+Shoot1)
JOYBUTTON2 - Left stick, D button (+Shoot3)
JOYBUTTON3 - Left stick, the weird push button on the front (+Turbo)
JOYBUTTON7 - Left stick, the E button (Activate)
JOYBUTTON29 - Left stick, the I button (+Brakes)

Mouse scroll is like 32 and 33, I think . . . I can verify that tonight.

Try installing qjoypad - very handy for mapping buttons, and it's the only way I could find to get the scroll wheel to work in Vendetta at all. I use it with the TargetLS plugin - just use qjoypad to map the scrollwheel to "[" and "]".

I actually have the full list of button mappings, including the mode switches.

Trigger stage 1 0
Fire 1
A 2
B 3
C 4
Pinkie switch 5
D 6
E 7
T1 8
T2 9
T3 10
T4 11
T5 12
T6 13
Trigger stage 2 14
Mouse click 15
Mouse scroll forward 16
Mouse scroll backward 17
Mouse scroll click 18
Coolie up 19
Coolie right 20
Coolie down 21
Coolie left 22
Throttle hat back 23
Throttle hat right 24
Throttle hat forward 25
Throttle hat left 26
Mode 1 27
Mode 2 28
Mode 3 29
i 30
MFD Function 31
MFD Start/Stop 32
MFD Reset 33
MFD Pg Up 34
MFD Pg Down 35
MFD Select Up 36
MFD Select Down 37
MFD Select 38