I've been trying to fix this for a bit now. The car idles rough but not all the time. It stalls once in a while, but it'll start right up. I hear a pretty loud hissing coming from somewhere behind the engine. I've replaced a couple of vac lines that were degrading and I think I still need to replace another one but I can't seem to locate it. I've got a 2001 ZX2. Can anyone help me find it?