ok i havnt entirely figured it out yet but what u need to do is get a blank image the size u need the picture to be and then then i supose load it up in xsi and go to application>views>textureeditor.
and i supose u need your blank image to show up here and then go edit stamp uv map.
I dont know XSI, but I'd assume there's some sort of "export UV map " option
I thought 3dsmax was the only company that didnt have that VERY basic feature built in (I know there's texporter, but I just find it weird they have to rely on a 3rd party to avoid doing the super crappy printscreen technique)
i managed to get a textured prop but it wasnt easy i had to export the model as a .xsi and then downloaded deep exploration to convert it to a .obj file then i downloaded uv mapper classic which isnt very good but uv mapper pro costs money. then i exported a uv map as palaner or however u spell it and then loaded the file in psp and put my textures over it. then i had assumed u load it back into the uv mapper software but i couldnt seem to do this so i just had to load the image into xsi and it didnt exactly work how it had looked like it would so i had to change the image but as it was a simple model it wasnt much of a problem.