Erratic Idle

I'm dealing with the infamous erratic idle problem, checked for vacuum leaks and found none yet the idle remains unstable, so i was wondering if the following 2 conditions can cause the idle to be the way it is.

1. On the Carburetors of an XJ550 there are 3 Plugs where hoses/pipes could fit, the most middle one I know is for the petrol pipe from the tank. What are the other 2 for? and do they need to be plugged?

2. I have 2 of the bikes Exhaust headers leaking, could they by any chance be contributing to the high idle problem?

Thankyou.

 

#2 YES! for sure that'll make you run lean.

#1 you mean throughout the whole rack there's 3 plugs? As far as i can recall, there's the one for fuel. and that's it. Well, the bottom of the bowls have the drains i guess one each for 4, and there's only ONE fuel barb between carb #1 and #2.

 

Kindly refer to the image attached. Between the 2 pointed arrows is the part I am talking about. I have 2 of these on both ends. Do they need to be plugged or do they remain the same as they are in the picture.

Thanks for the previous answer. I have to get 2 of the manifolds tapped, will report back if that helps.