My buddy has a 01 si and it caught on fire last week so i went over this weekend to help him fix the car. He cut the distributor plug off on the engine wiring harness and when he went to replace it he was missing a wire. There is 9 wires on the plug but he only has 8 wires hooked up right now. He is missing the blue wire. Any ideas where this wire would be at and what it is for. Here is a pick it is the wire on the far left.

 

Is it an 00 or 01 Si?

The 00 Si neither needs nor uses the blue wire in the distributor plug.

 

its a 2000 civic si

 

Should i just cut the wire then

 

It looks like you have 2 blue wires in the pic. Is the wire missing from the dizzy or vehicle harness?
RPM wire is always blue. It runs to the under hood tach plug in drivers side rear corner, then thru the firewall to the gauges.
Some OBD2 cars have a second darker blue wire for CYP output. That one runs to the ECU. Maybe you could list the color of the wires you have.