heat only blows out of defroster
 

Just bought a 95 Blazer, with the understanding that there were multiple minor issues with it. This one has me slightly stumped however. My heat only blows out of the defroster vent (which I understand is the default when there is a vacuum issue). After some poking around on the forum and under the hood, I found the hose coming off the back of the upper intake manifold lead to a "T" fitting which the previous owner had apparently put 2 screws into. My question is, where are these lines coming off the T with the screws in it supposed to go to? And I suppose also any reason you folks can come up with why the screws might be in this T-fitting?

Pic of the T-fitting with the screws in it: http://i46.tinypic.com/2j1absg.jpg

It's the clear hose (lower in this pic) off the back of the intake manifold that leads out to the T-fitting with screws: http://i46.tinypic.com/5nsruq.jpg

I have a 98 but that looks like the "T" fitting that's by the drivers fender and master cylinder, one end goes into the fender to a canister I think. I don't have pics on this computer but let me see what I can come up with here in a bit.

Does this help.

Here are some pics and diagrams from my 1996 Sonoma 4x4.

Both those posts are exactly what I was looking for. Thanks guys. It's dark now, but I have tomorrow off so hopefully I'll have some time to check this out on my end. I'll post what I come up with for results. Oddly enough, given where these vacuum lines run to, my 4WD works fine.