Ok, I got a bum EX with no Tach. I am flat broke so asked my Dad if he had any aftermarket tachs lying around (Domestic drag racer in his day). He lent me one off of his drag car (66 Chevy Nova SS). Anyways, its a monster tach (NO, I dont want a giant tach on a stock car, but I need a tach) and in the instructions it says for 4cyl cars to snip two wires. I'm not gonna keep the tach and will give it back when I can afford one.
Geez, finally the question...

What will happen if I DONT cut those 2 wires? Will the tach work at all? Any idea how much it would be off?

Thanks