My F800GS is now two and a half years old, done 48,000 miles and it's great 
Fitted an Akrapovic exhaust some time ago, half the weight of the original and a nice sound ... but could do better
So cut the removable baffle in half
Without the baffle it looked errr mmmm naughty but nice
But had a crisp bark to it that was tiresome on a long journey
So now I drilled the shortened baffle
The exhaust sound good but not too naughty and the escaping gasses suck out the other gasses through the small holes and unleashes loads of extra power to reel in the 1200's
1) Baffle cut in half
2) Extra power releasing orifices

Fitted an Akrapovic exhaust some time ago, half the weight of the original and a nice sound ... but could do better
So cut the removable baffle in half
Without the baffle it looked errr mmmm naughty but nice

But had a crisp bark to it that was tiresome on a long journey

So now I drilled the shortened baffle
The exhaust sound good but not too naughty and the escaping gasses suck out the other gasses through the small holes and unleashes loads of extra power to reel in the 1200's

1) Baffle cut in half
2) Extra power releasing orifices

Get it on the dyno ASAP and have the AFR's checked. You don't want to be melting pistons.