i got a vaccuum guage for christmas from my sister (i wanted a voltmeter but you know what women are like when it comes to technical stuff). i would go back and change it but she bought it from some little place up north and its gonna be too much hassle to take it back so can i wire it up to me 1.4 spi astra?!? i've been looking at the instructions and i am confused. would it go on to the back of the injection unit housing, where there are 2 vaccuum pipes which already go in?!?