Toyota Repair: random misfire, toyota avalon, timing belt

Question
QUESTION: 1997 toyota avalon xl , 124 k miles.automatic.
I changed the timing belt and water pump.
it had some misfire before and changed the spark plugs and ignition wire(dealer items).the misfire was gone, after a week it did came back with different codes.
random misfire p0300, sometimes cylinder 2-3-5, after clearing the codes still random misfire p0300, 2-6.
thanks .
ANSWER: Were these misfire codes present before the timing belt was replaced or did this happen after the belt replacement.


---------- FOLLOW-UP ----------

QUESTION: yes the misfire codes were present before the timing belt was changed.i checked the timing it still perfect.


Answer
Thgere are known problems with the igniter coil packs, each coil fires two cylinders as follows: 1+4,2+5 and 3+6,if one of the coils has a problem it will affect the other cylinder as well, the coil packs are located on cylinders 2,4,6 a code of 2-6 doesn't seem logical it should be 3-6, try replacing the #2 coil/igniter pack and see if it solves the problem.