1) ditto on the Raptor unit; but BEWARE of cheap knockoff's on Ebay and elsewhere. Use only a REAL Yamaha unit. Available from Eaglemike or Yamaha (and perhaps elsewhere)
2) I share Tom and others' distaste of the factory vacuum unit; like him I've had many bikes (this last one is #39) and the vast majority have had manual petcocks. The stock Vacuum petcock is in the top 5 failures on a stock KLR (scientifically proven by me! ;-) )
3) I've heard of people swapping "straws" between the KLR and Raptor petcocks but I haven't done it....some said it was impossible to do without crushing the straw others claim to have done it...personally, I don't care about the smaller reserve, especially with my translucent IMS tank: I can tell how much gas I have left from 20' away!
4) several years of University physics tells me Damocles is correct.....though he doesn't need my validation on this! LOL