I also have occasional misfires with my S14.
Try the following things:
Change fuel Filter - could have some dodgey stuff sitting in there.
Check the screws are on tight which holds each coil down (dont do them up too tight that they snap).
Check the vacuum lines for leaks etc.
Check 02 sensor (check for voltage on the multimeter. from memory I think it should have a charge of >0V to <1V - tell me if its different values.
Reset ECU (just disconnect the battery for 30 mins and press the brake a few times to get rid of any remaining charge)
Check/block your EGR valve, this has the tendency to make the car "hesitant" at lower revs, if you want to block it visit this website
http://www.jull.co.uk/mods/egr.html
Let me know what the culprit is with it mate.
Good Luck
edit: what plugs are you using, are they hot, cold or standard rating?