I'm trying to figure out which vss I am suppose to use in my T5. I am converting over to speed density and had heard I needed to switch out my old vss for one for a sd car. The problem is that GM has two vss's for a '91 T5. I am assumming they are based on rear end gear ratio. I have an '87 GTA using a 9-bolt w/ 3.42 ratio. Do I really need to switch and if so which part # do I need to switch to?