Red tube/stalling when sudden throtle
 

I'm working on a 2004 (?) 500 Polaris H.O. for a friend as a favor. I changed the starter and bendix, and put it all back together. I noticed that there is a long, red, very small diameter vacuum (?) tube coming from the bottom of the carburetor that is not connected to anything. I'm sure it should be, I just can't see to what.

Additionally, now when the machine is at low idle, and I suddenly throttle it, it stalls or causes a strange backfire? in the airbox (I feel it under my seat). It did not do this before. Otherwise it runs great.

I'm wondering if these two things are related. I'm new to working on ATVs so any help you could give would be greatly appreciated.

Tube should just be the drain/over flow tube from the carb bowl. Shouldn't have anything to do with the back firing,but could be carb related if it's running lean or even if it's a little rich.Or even a cam problem if earlier than a 2004 model. Knowing the year model would help more. Should be a 17 digit vin # on the left frame behind the a-arm.10th digit is the year model.Plus if it still has the engine sticker on the recoil housing,the first two numbers are the year model.