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Do aftermarket exhaust systems effect jetting?

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I have always used the stock exhaust (with promoto spark arrester) on all my bikes (thumpers anyway) because I cant really use more power. On my new bike I want to install the FMF Q4 with a power bomb header. I already have the exhaust, my main motivation is to quite the bike down and to have a spark arrester.

The bike is an 07 CRF450R and it is all stock (brand new) right now. I am going riding this weekend and I am going to try to go and ride at a private track with the stock exhaust first so I can see how it runs and break it in with the stock equipment. The following day I want to go and ride some trails with the new exhuast.

My friend added an FMF Q2 and power bomb header to his 06 450X and he said he had to change the jetting on his bike. I asked the parts guy at the Honda shop (when buying the exhaust) and he said I won't need to change the jetting on my bike. I called FMF and they said 2-3 sizes larger on the main and one size larger on the pilot.

I am thinking I will just run the new exhaust and see how it runs but does a new exhaust system usually require rejetting? I am trying to see if I need to bring jets with me and plan to tune while heading out this weekend. Sorry for the dumb question, I tried to search this out first.

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