1998 Subaru Legacy engine not ideling

I have a 98 subarue legacy gt limited with a 2.5 boxer engine I recently lent my car to a friend and he drove threw a water puddle an drove it about two blocks after started running funny an called me I went and there was a headlight that came out of the casing and the bulb blew an was laying in water I dont know if that screwd the computer or if there was an open circuit an the water shorted it out at first it would crank but not start so I let it sit an came back the next day an it started an ran fine till I got home them it died I took out the air filter an the coil pack wires an dried them off an it starts every time now an as long as I leave it about 1000 rpm it will drive fine to but when I go to stop it dies an it starts right back up fine an when I turn at low speeds there is a jerk type feeling that I dont know what it is but at higher speeds does not jerk.
CAN SOMEONE PLEASE HELP ME!