These are in order that will typically give you best ‘bang for the
buck’ as you go and get progressively more expensive. Generally you
shouldn’t start mods in the next stage until you’d done everything in
the stage before.

STAGE ONE

Free Flowing Rear Muffler box
The brand is not important but a good design is not overly ‘loud’ while
still providing good flow. I good trick is to use a 2 1/2 in/out
muffler box

Pod Filter with Improved Cold Air Intake
Brand is not that important as any pod filter will outflow the
factory panel filter. Popular choices are K&N and Simota. Cold air
intakes can made from a large diameter pipe ducted to the front or by
fitting a bonnet scoop.

Exhaust System 2 1/4″ or (2 1/2 for 2L V6)
Mandrel Bent system is best but is a more expensive option than press
bent. If going press bent, increasing pipe size to 2 1/2 is an option,
but a mandrel bent 2 1/4″ system is optimal for road driven cars.

Headers 4-2-1 or 4-1 Style
Generally both of type will give improvements accross the rev range.

Rechiped factory ECU
Available for 1G owners only.

STAGE TWO

63mm Throttle Body
The stock 60mm throttle can be bored to 63 very easily and gives very good gains

Fuel Pressure Regulator (optional)
To compensate for larger amount of air available, you will need to at least increase fuel pressure slightly.

ECU
A programmable aftermarket ECU will get the most out of the
modifications done so far, and will be required if you want to go
further still.

Injector Upgrade
By now your injectors will probably be operating well beyond the 80%
duty cycle so its time to upgrade them something larger. GSR-T 390cc
injectors re a good choice and can be had 2nd for cheap. Best done at
the same time as the ECU upgrade.

STAGE THREE

Exhaust system 2.5″
To get the most out of the next stage you will need to free up the
exhaust even more. This may result in a reduction in low rpm
performance, but by now your probably going racing and gains up top
will be worth it.

Increase Compression Ratio 12:1
Required to get the most out of the camshafts.

Camshafts
JUN or RPW offer racing camshafts. Two types are available to suit
race or rally. Regrinds are also an option if on a tight budget.

Pistons and Rods
Lightweight pistons and rods will potentially allow higher RPM. Not much off the shelf, so they will have to be custom made.

Crankshaft
Knife edging, and fine balancing all the moving components will
reduce parasitic losses and increase reliability at sustained high RPM