Toyota Repair: Cylinder misfire, cylinder misfire, cylinder fuel

Question
I have a 96 Toyota 4-Runner that has the following problem:  Cylinder
#4
misfire. Code 0304 (I hope I have that correct).

The check engine light came on and would randomly flash.  After about
15 minutes of driving it starts to miss.  I've had it in for repairs
and
am on my third time of taking it in to the same place for the same
problem.  They are stumped.  This is what they have done so far:

Day 1:  Changed all spark plugs and spark plug wires, change air filter
and oil change.

Day2:   Swapped coils around (1 coil per 2 cylinders)-no change.
Changed No 4 cylinder fuel injector.

Day 3: Did compression check on all 6 cylinders(ok) changed spark plugs
again and other things I'm sure. No help. Checked electrical signal to
fuel injector(ok). Saying appears to be computer issue-unknown.

Thank you.

Answer
After all that I can only think of the possibility that the number four cylinder was not correctly identified, it's located on the left cylinder head(driver's side) in the middle, cylinders 2/4/6 are on the left and 1/3/5 on the right side, let's make sure they are working on the correct cylinder, I know it sounds too simple but I want to make sure this is not the case before going deeper into this, please follow up and let me know. I may be on a short vacation and not back until monday but you can get back to me directly at <tedrttr@yahoo.com>