Question about the exhaust of a Yamaha TDM 850 Model 2001

Hello I am George from Athens/Greece and I'm a (very happy) owner
of a Yamaha TDM 850 Modell 2001.
After asking several yamaha-authorized mechanics here in Greece
I didn't get a clear answer to my question.
Everybody has his own opinion!!!

The Question:
I'm thinking about changing the whole exhaust system with an after-market
exhaust system.I want it to be be a 2-2 system,that means with 2 end-mufflers.
But........
If i put a 2-2 system on my bike i will have to remove the collector can
and there is where the problem starts.
Will i have a lack in Torque or Power if i remove this collector can ?
If yes....in low or high engine rpm's ??? And why?
Why is this collector can so necessary???
What is its purpose ???

I would really appreciate it if you could give me some answers.
You are really my last hope.
Many Thanks in advance
Best Regards......