Yes. When you come to get quotes for next year's insurance they ask if the car has been modified and re-mapping comes under "engine". Don't be surprised if lots of companies won't quote unless you ring up ie, they won't quote online.
. . . and don't be surprised if there's a hefty increase in your premium. Telling an insurer that you've had an engine re-mapped makes them think 'Petrolhead!' resulting in them charging you a 'Clarkson premium' ;-)
I think you should also read your current insurer's Terms & Conditions. They probably require you to tell them of any modifications mid-term (on the basis that you could take out a policy today, modify your car tomorrow and get 364 days of cover at a reduced rate).
Doesn't affect my premium at all, surprisingly. I have a Volvo and have a Volvo chip fitted. As part of the blurb they said that Volvo's own insurance didn't charge extra so I was prepared to argue with my own company (LV=). As it happens I didn't need to, although I did make a point of telling them that the top speed wasn't affected by the change.