My car idles funny, goes 800 then 1800 rpm then back down, etc.... does it when the car is warm or hot!

I reset the ECU and it idles fine...then a few moments later...bam same thing happens...Here's the story:

I got a new STR Manifold. Everything is hooked up correctly...except for the sensor on the BACK. I believe its the IACV. It has two water hoses going into it and it has 2 holes...one that reads manifold pressure, and the other one, i'm not sure what it is?

Anyways, on the STR Manifold where throtte body and manifold mates, there is the 64mm hole and there is SUPPOSE to be another hole for the plate (Air from before the throttle plate) but on the manifold it does not have that! That hole provides air or something for that Sensor on the back of the maniofld....but now there is non.

However, on the STR manifold, it has this nipple taht sticks out for air to go into that 2nd hole on the sensor. am i suppose to connect that to manifold pressure? This one guy said to leave it open...

Help! Help me idle fine again!!!

 

Oh yeah when it idles funny it makes a hiss sound ...like this:

"Vroooom!....hissss!.....Vrooooom!.....hissss!.... ..Vroooom!!......hisssssssss!....Vrooom!....hissss sssss!"

 

I hope this clears some things up! THE IACV (The Mesh Part) is getting no air into it. That might be my problem, but i'm not sure

Heres the bottom of the manifold:


As you can see that nipple part I did not connect it to anything! I have no clue what I should connect it to.