KA is running shitty

[Flicktitty]

hey guy's, i'm having a little bit of a problem on my girlfriends 240sx

(1991 240sx KA24DE Automatic 155K miles)

the car has been running rough for the last week to week and a half.

it seem's to be "missing" but we did plugs, and wires on it and that didn't do anything. car seems to be lacking some power but nothing major, haven't noticed any change in gas mileage. she usually runs the car on 87 but we ran a tank of 93 through it and that didn't seem to help it much. the car almost sounds like a WRX.

there are a few major holes in the exhaust so i thouhgt maybe a back pressure problem, but the car has died 2 times now, One time in park it just shut off, and another time in drive sitting at a stop light.

the car seems to idle at about 6-700 then drop down to about 400-500 and sometimes to about 200-300 and sometimes kicks back up. didn't know if it could be a cap/rotor? or if it's a fuel issue (bad injectors or a clogged fuel filter/screen?

the car hasen't thrown any CEL or anything so thats not being much help. i just don't want to throw money at it and it not be the problem since she is thinking of getting rid of it in the next few months.

thanks much.