Possible Vacuum Leak

I have a 93 Eclipse GS manual. After the engine's warm and I press the clutch while stopping or put it into neutral, then RPMs drop to about 400-500 and sometimes even cut off. I was thinking it might be a vacuum leak because it only started after I put my car bra on upside down and the engine kept overheating (dumb mistake.) Any suggestions?

My car used to do that about 3 months ago. My problem was a faulty idle screw. The screw would go in and out... so while driving the rpms would drop down and cut the engine then turn back on etc etc. Try turning your idle up a little bit and see if that remidies it.