Intermittent Misfiring on Pajero io

Mitsubishi Pajero I.O. 1.8ltr 1999, 114,00kms.

Problem description
When the car is put under load from either driving up a hill with
passengers or sometimes just having the air conditioning on the car
stops
firing on all four cylinders and reports an Error Code #44 (Coil -
cylinders #1 and #4). The car rumbles, loses power and the engine
warning
light comes on. I pull up turn off ignition and re-start and
everything
will be OK again for a while, again until under load. The load point
at
which it trips has varied greatly in the six months this problem has
persisted.

Work done so far:

1. ECU sent away for testing and came back fine.
2. All connectors checked.
3. Fuel filter replaced.
4. Plugs changed.
5. Plug leads changed.
6. Coils swapped over and error code still reports 1&4 as not firing
(therefore assuming coils are fine?).
7. All four injector connectors replaced.
8. Oxygen sensor replaced.

Current condition (as of 7/4/07)

Now the problem mainly occurs when first driven in the morning.
Within
30 seconds of starting the car up it fails at around the same spot,
just a few yards up the road. Maybe its starved of fuel? On restart
again
its fine. Coming home from college after the car has been sitting
still
all day I sometimes get the problem, but always worse in the morning.
What I find odd about this is how the symptoms of the problem appear
to
have changed. Six months ago driving uphill could set it off, then
puttin on the A/C would almost guarantee it failing, now the A/C will
operate, though you feel power loss. Its now happening initially
starting up
within 30 seconds I'll have the problem. Ive spent$1200 trying to fix
this, I'm now back at college as a mature student after being made
redundant, so would really appreciate any help you may be able to
offer.

Many thanks,