power & running issues MCV36R

[BigBadBobsie]

Hi I have a 2003 MCV36R Camry SPortivo, Australian spec. have owned it for 12 months. Have had power issues.
replaced:

plugs
fuel filter
O2 sensors (engine)
MAF sensor
Throttle Position Sensor
Have checker EGR valve - all looks good
Have coded OBD II, no codes coming up.

Current issues are:
Flat spot/s from 1000rpm to approx 3000rpm (esp on gear change from 1st to second)
Once flat spot stop, it powers up enough to throw you back in your seat.

Also, rough running when sitting on constant speed, esp bad between 65-85Km/h.

any suggestions where to start looking next? almost ready to set it on fire or pay up and let toyota replace everything possible...

Have recently done a 800km trip. half way through, isolated the EGR valve. Running probs have improved greatly, but still lacks power.

[leakyseals]

The vvt-i will kick in at higher rpms, if the cam gear sticks you may feel a flat spot in acceleration.

[BigBadBobsie]

the flat spot is quite large as in from 1500-3000rpm and very consistent. after posting that it has been better, today it has reverted to same old lack of power.
A friend has suggested injector issues? would this be plausible?

I also run a 1998 MCV20R with same 1MZ-FE engine and just changed the plugs. i have now got Bosch 4501 Platinum plugs in both. I checked the Denso (genuine) against the Bosch and the firing post is a good 3-4mm shorter on teh Bosch plugs, which i imaging may change the combustion pattern. I havent noticed a drop in power or anything et in the old girl. but thought it unusual that the plugs would be so much shorter. (body and size etc were identical. just the firing point would sit closer to the head with the Bosch plugs)

[leakyseals]

The difference in the plugs may be Iridium vs Platinum. Over here the recommended plug is denso or NGK Iridium. More efficient combustion, requires less voltage to fire a spark so its easier on the coils and electrical system, last much longer, 80k or more. Suggest you start with a change to a 5w-30 synthetic oil and perform a couple of fuel system cleanings with PEA additive. Not sure whats available.

[BlackCamSe]

Is it misfiring? The coils are known to fail on these cars.