If it turns out not to be the external spring on the clutch yoke then check the spring on the pedal assembly. As much as I'd expect you to be able to sense it happening at the clutch pedal, it is an annoying squeak that I've had there in the past. The pedal assembly is buried behind the underdash panel and attached to the firewall so it's possible that's misleading you where it's coming from. With a good light, look at the clutch pedal and the return spring for the pedal. Using a slot screwdriver, pry the tails of the springs over just a little bit away from the frame. Does the squeak change? If so then you know that's it. The spring will likely soon return to its original position and start squeaking again. I pried it over and applied some grease to the contact area. I vaguely recall having to repeat that occasionally until the noise finally decided to stay away.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now