heres a way to look at it.. vacuum equals no air.. altitude equals less air... sooooo ya go up to about a bazillion feet altitude, no air, hence a vacuum..... altitude also affects boiling point.. at albqqqqq altitude of 5500 ya say,, id guess the boiling point of water is about 200,,, oh.,,,ps... ya also need to change your timing with alititude.. run more advanced with more alititude if i remember right....
i never time with a light or to specs anway... just run it as far advanced as ya can without pinging...or starting problems when hot...
