Cracking/perishing is quite common on older bikes as I mentioned before, but I've never seen it before on as new a bike as an XT660Z!?

Leaks here will affect the performance of the engine as un-metered air will be drawn in to the inlet. How badly performance is affected depends on how bad the perishing is and the size of the leak.

As a stop-gap you can seal them up with silicone mastic, which works for a while until it start s to peel away. Essentially you are going to have to fix it/get it fixed. It is only going to get worse in the long run.

BTW, how old is your Tenere?

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