Before fitting a power Chip/Module Definitely consider fitting a 2.75" Exhaust System before the "CHIP". A good friend of mine used to work for Beaudesert Exhausts and he was telling me that after the Larger Exhaust was fitted most were more than satisfied with the Power increase not opting for the CHIP. From my own experience of at least 4 Turbo Diesel Powered vehicles over the years that the increasing of the Exhaust size especially with TURBOS can give an increase of up to 20% Power/Torque Figures on the Dyno. 

With a proper Dump Pipe Collector and larger system the Turbo Spools (spins up) quicker giving better low down power and the Exhaust Gas Temps at the turbo are lowered under Full Power.

Hope this helps with your question.

Cheers Kev.

Hi TA,

We had the same problem with our old 97 V6 petrol. 455,000km.40 kmh up hills towing 1870kg

In Dec 2012 up graded before our pending retirement to a GX 200 series Turbo V8 Diesel cruiser. now 100kph up hills  Better Fuel economy Total.

Jim & Eunice

That's where turbo tech comes into it these days .. Bigger exhaust allows turbo to work better .. Best not to fit an extremely baffled muffler also... I fitted a Develsown.com water/ meth injection system on our 6.5 GM to keep inlet temps down on hot days on steep hills.. I found it has cleaned combustion chambers etc only comes on at full throttle .. Bigger exhaust is a win win no negatives..