Problem with Shootmania Storm (Instagib)

[Letnis]

Hi guys,
I have this problem with Shootmania, i go normally playing instagib and then when they come a lot of people in the server (Like Full Server: 12/12), i begin to go in spurts and really slow, my connection it's really good, i do always 45-50 ping and snapshot on 70-80. Cause of that i see other people going slow and me too, an exemple: I was at the jump, after 2 seconds i found me behind the cage!
Some friends gave me the advice of disable P2P, i disable it.. But it's always this problem!
Normally when i play on Elite, Combo, Joust isn't this problem! Only on Storm when i play Instagib, Obstacle or Siege with a lot of people cause me that! Are solutions?

Thank you if u answer!

[XuL]

Whats your fps? If its under 60 or something try turn down the graphics.

[Letnis]

Fps on instagib: 95-100
Fps on elite: 110-120