What bike are you troubleshooting, the 550 in the avatar?
What is the throttle position when the "bog" occurs?
Can you characterize the plug condition amd color?
Is your exhaust stock?
Have the carbs been rejetted, needle position changed?
Where is you pilot screw setting?
What is the set up number stamped on the carbs?
The K&N is a better setup than pods IMHO. But, it may still be less restrictive than the stock paper type.