If you want to get the best, performancewise out of the bike from fitting termis then you will need to do something, reflashed ECU, powercommander, I'm not sure if there is an official ECU option for termis for a 998 BIP.
I made a few mods to my 998 without and change of ECU, did away with the intake mesh, cams dialled etc then had the Air fuel ratios (AFRs) checked on a dyno, they came out as economically lean
, so no need to do anything unless unless I wanted the last few BHP/lb ft of torque.
The noise limit at the trackdays you want to do will determine if the bike is too lound with termis.
You should be OK at any 105db day, my 998 is well under that with 50mm termis.
Any noise limit under 105db could be a problem depending if/how they test the bike.
Various tracks have different limits, check with the organisers of the days you are thinking of.
Ray