You should not call
preTrans on every update. You only need to call it once when you initially setup the link.
Code:
import viz
import viztask
viz.go(viz.HMD | viz.STEREO)
isense = viz.add('intersense.dle')
track = isense.addTracker()
main = viz.link(track,viz.MainView)
main.preTrans([xoff,yoff,zoff])
def mainLoop():
yield viztask.waitKeyDown(' ')
#Do Stuff
viztask.schedule(mainLoop())