Idle Problems???

[aurilius_maximus]

I am having some weird problems with my 96 Cobra. This morning when I went to start it up, it was very hard starting, taking twice as long cranking before it kicked over. Then when it was running it was idling extremly rough, sounded like it was way to rich, but I dont know for certain. I proceded to give it some gas for a while and that seemed to smooth it out a bit. Then I pulled out of the driveway and went maybe 3 miles when I stopped it almost died, dropping to under 500 rpm's before it caught itself. After it was fully warmed up the idle smoothed out, but it was still hard starting intermitently. Also dont know if this is related or not but I noticed when I shut the car off, I hear a hissing, like a vacuum leak, dont know if it has always been there and I am just now noticing it or not. My car almost has 30,000 miles on it, and I recently replaced the sparkplugs, wires, and both fuel, and air filter. If anyone has any idea on what I should check it would be most appreciated, thanks in advance...