2000 cougar dies in idle!

[Fate544]

Its the '00 2.5 L 6 cylinder manual transmission with 120,000 miles, I haven't really had any problems with the car, except that recently whenever I put the clutch in to slow down for almost anything, the car will just quietly and calmly die, no sputter or sounds that I can hear or vibrations that I can feel, the engine just turns off, and if it wasn't for the loss of power steering as well as the inability to accelerate, I wouldn't even notice. It started doing this very rarely, but its so common now that after I drive the car for 2 or 3 miles, it will do it any time I put in the clutch for longer than a moment. It's worse as the gear gets higher, as in, it will do it almost every time I stop/slow from 3rd or 4th, and less often as the gear goes down. It also looses a ton of horsepower and jerks a little if I run the air conditioning while I drive it. That's really my only symptom, I'm in the middle of doing the normal maintenance, as in spark plugs&wires, changing the fuel filter, etc. My check engine light has been on telling me I have problems with both of the cats, as well as my EGR valve, and my wiring. I replaced the EGR valve, cleaned out the tube it connects to, and I had both cats tested. They are supposedly fine, so that leaves the wiring. I was in a wreck recently, a very minor wreck and these symptoms occurred before the wreck, although it did damage the hydraulic shock that the engine is mounted on; could that contribute to the problem? I know I need to replace it, but it still has most of the fluid and I had a mechanic say that it would be fine to drive for a while. oh and one more thing, yesterday, my brake lights just started being on continuously, whether or not the brake is being used.... any suggestions?

P.S. The wreck was a front end collision that only managed to bust out both headlamps, bend the hood and crack the bumper cover, no frame damage or anything, and it has all been replaced (excluding the engine shock), so I don't believe it affected the engine at all.

please help!
-Alex