well there is a function for resetting player max speed if you could search...
PHP Code:
new Ham:Ham_Player_ResetMaxSpeed = Ham_Item_PreFrame
public plugin_init()
RegisterHam(Ham_Player_ResetMaxSpeed, "player", "PlayerResetMaxSpeed", 1)
public PlayerResetMaxSpeed(id)
set_user_maxspeed(id, 400.0) // whatever speed u want