Tach on a 1998 S-10

I have  a 1998 Chevy S-10 with the 4-cylinder 2.2L engine. It is the 5-speed version. The truck did not come with a tach from the factory so I bought a Sunpro Tach and I am having trouble locating the correst wires. The engine uses a distributorless ignition system which uses a waste spark to turn on the engine. This site says that the wire to connect the tach to is white but I cannot find the white wire that it is talking about. I bought the Haynes book for my truck but it doesn't give me a diagram of the PCM (powertrain control module). I need to know where to find the white wire or whatever wire it is that i have to connect my tach to. Any help would be greatly appreciated.

Well, mine said that my tach was a blue/green at the distributor.  I didn't want to go through the firewall, so I actually found the same wire behind the driver's "knee" panel to the left of the steering wheel.  To make sure if was the correct wire (even though it was the same color) I tested it with a DMM (in AC mode), and it fluctuated as I pressed on the gas.  So I used that instead.  You may be able to find it under your dash, maybe above the fuse panel or just probe around in a mess of wires.  Just an idea.