I'm getting the SI vacuum distributor for my ZC because a friend of mine that works with the ref at the college told me that he wont pass me unless I have EVERYTHING SI. So I have to hook up the hf wiring harness to the si vacuum box. Something is different between the SI vacuum, and the HF harness...but not to sure what. anyone? I'd be able to find out, but my vacuum wont be shipped till tomorrow.