fans turn on, engine bogs down at idle

[90 GSX]

My idle has always been rough, I think it has do with why my car is knocking a little bit somehow. I have one of those infamous small random pops out the exhaust at idle. Why is though that when my fans turn on the engine bogs down and starts popping like crazy even more. The only boost leak is from the tb shaft seal and its small. I just put the aircan on so its not sucking the hot air in. What causes this problem?

[Jake90GSX]

One thing that can cause an engine to "pop" out the exhaust is the timing being slightly off, I would definately look at that, the engine bogging down a little bit is normal when more stuff is running, such as the fans and/or AC, what is your cars RPM before the fan is on, and then what does the RPM lower to once the fan comes on and its bogging.