weird ISC problem

[10fold]

I have been having idle problems recently and decided to go after my ISC. I took my brother's ISC off of his 91 Laser RS and tested it. It tested to spec, around 29-32 ohms between each of the coils. I took mine off of my 95 TSI and it tested around 40 ohms between each of the coils. I decided to switch the ISC's but this made my idle even worse. I started my car up and it ran perfectly fine for about 10 minutes. Then it started surging even worse. My idle is bouncing from like 1200 to 1800 or 1900.

So, while I'm waiting for my car to cool off so I can put my ISC back on, I decided to ask for your help. Should I just get a new ISC or is there something more serious wrong? Thanks in advance.

 

[10fold]

Hmm...apparently my original ISC was a black top one and was replaced. According to this, it's supposed to read around 40 ohms across each pin. http://www.dsmisc.com/dsmweb-dw/faqs.html

So I'm guessing the coils are actually good, but am I supposed to be able to rotate the plunger thing, the part thats on the opposite end of the coils? Oh and sorry for the double post.