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!