performance upgrade

I've a F23 motor in an Odyssey and would like any advice for upgrading its
performance. I'd like to increase its midrange torque mostly as we find it
gear hunting a lot on long hills at around 100klm/hr.
It also kicks down too easily at middrange revs, even if it only has 500rpm
remaining to the redline.
Has anyone good or bad experience with chip upgrades, exhaust systems and
other bolt-on mods etc, or should I be looking for more extensive work such
as a supercharger?

 

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Helpful info you could provide: the year of the vehicle, the mileage, as
well as the market (country).

'Curly'

 

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Helpful info you could provide: the year of the vehicle, the mileage, as
well as the market (country).

'Curly'

 

Yeah cuz upgrading a minivan is the coolest thing since peanut butter!!

 

Its a June 2003 manufactured Odyssey - the last shape before the current
lower "sporty" shape.
42,000klms.
Sydney / Australia.