I'm a noob here, so bear with me.
I looked around for quite a while trying to solve the deteriorating vacuum line problem. Finally I found a good replacement. They are 5/32" OUTSIDE DIAMETER Nylon lines from MSC. They are selling similar nylon lines on ebay, but nobody could touch the MSC price and they sell by the foot. I got Red, Green, Yellow, Blue and Black for .12 per foot plus modest shipping. Here's a link to the Red: http://www.mscdirect.com/product/48635932
I had to use blue for the pink Thermacter Bypass line. They have natural off white color I could have used, but I noticed the lighter colored lines in my truck seem to be the first to deteriorate.
These lines are rated at 170°F. I wish they were rated a bit higher, but it's been about a month, and so far they still look like new.
It's quite possible these lines will work on other years, but they will definitely fit the stock rubber fittings on 1993, and I strongly suspect 1992 1994 1995 1996 if not more.