It's more important to mention a remap to your insurance company than anything else.
Say a kid runs out and you have no way of avoiding him/her. Although you were within the speed limit etc, he's killed. But it's clearly not your fault. However, you didn't inform your insurer of your remap. You could then find yourself in very serious trouble: The police as standard procedure in a fatality may impound your car and inspect it very thoroughly. if your undeclared remap is discovered your insurance could become null and void. You could be facing some very major claims.

Wise words them... A friend of mine fell foul to something similar which ended with him loosing his job, his car was impounded for 6 months and one failed suicide attempt (well glad he failed that

)
Driving down the road happily minding his own business when a Civic TypeR pulls out on him, mate pulls round the slow moving car only to be overtaken 20 seconds later by same Civic. 2 mins down the road my mate comes round a bend to find an accident, civic had killed some old lady - several witnesses claimed my mate was racing the Civic (which didn't stop) police popped round to his house in the middle of the night, arrested him and his car was impounded for 6 months, during which time my mate was on police bail for causing death by dangerous driving, he lost his job as he couldn't drive anywhere (painter& decorator) and the stress & worry of going to prison, coupled with not being able to pay the bills etc... was too much for him to bear.
Fortunately the civic driver was found, went to court and my mate was cleared by the jury, but Imagine how much worse it could have been if his insurance was voided for not declaring something.