I'm sure all XTZs produce the same amount of waste heat per unit of energy used for a given state of tune, there is no logical reason why they shouldn't (unless something is badly wrong of course). The heat from the headers and collector is not dissipated well on off-road bikes because they are tucked in close to the engine (good for ground clearance). This considerably reduces air-flow. Not good for cooling. The plastic lower covers don't help either.

No one ever complains about the X/R because the headers hang out in the wind and are effectively air-cooled. However, as soon as folk fit high level 2-1 systems (Metal Mule/OTR etc) they start complaining of an excessively right leg for the same reasons as some Z riders get hot left legs. (Plus obviously the fact that the pipes are closer to your leg!)

It is down to the design of the exhaust system and it's routing - it's a compromise. As it's an off-road orientated bike, the designers have to work round what's best for styling, ergonomics, ground clearance, gas flow and cooling. Something has to come at the bottom of the list of priorities!

The determining factor with people who complain seems to be ambient temperature, and I'm sure you just coming to the end of a long very hot summer in Chile. In the UK and northern Europe nobody ever complains about it. It would appear that riding in temperatures in excess of 25C the headers just don't get enough air flowing round them, and what there is relatively hot. The temperature differential between the ambient air and the surface of the pipework is too small to allow heat to dissipate. In the northern Europe the air is cold enough all year round for the it's cooling effect on the exhaust to be sufficient.

Also remember in hot climates the fan is going to operate a lot more often and that will blow even more hot air over your left leg!

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