On my 1987 TPI harness, there was a plastic type material holding the wires in place near the plug for the ECM. Well, if you want to completely remove a wire from the ECM plug, you can't get by this plastic stuff.

Here's the trick...
When warm, that stuff is kinda soft, but when cold it will crack! I was able to crack and chip away at this plastic stuff at about 25 degrees. My TPI harness is in my S-10 and I'm converting from MAF to speed density so I want to pull a few wires and make a nice job of it.

Not sure if this is helpful, but if anyone is looking to pull wires from the ECM (like conversion from MAF to speed density), then you now know of one way to get the wires out of that plastic stuff.

Good luck

 

If you are doing what I think you are doing, they make a tool for that...makes a neater job of it.

 

Good info.. I heated mine up with a heatgun and made a holy mess out of it all. Didn't think to freeze it. Of course it was like 90° outside at the time I was doing it.. I supposed you could remelt it and pour it back once you've inserted/removed the wires. I was going through the same thing when I coverted a couple harnesses to SD.