1995 Ford Taurus Erratic Cruise Control Problem

Hello;



I have a 1995 Taurus GL wiht 3.0 L engine.

The cruise engages, but "surges" up and down about 5 MPH when engaged. I tested the Servo using the Ford manual and tested the three resistances within, and they were within spec.

So. Where would I find where the problem lies?

Also, WHERE will I find the VSS, and where is the Amplifier? I looked and looked for these but no luck.

thanks