Can any one tell me what the line is in this picture? the line with the white arrows pointing to it lower left . It also has a green cap on it and what would happen if it's not hooked up to anything.

 

That is the vacuum line for your vacuum assisted power brakes. You will have a huge vacuum leave on the car causing things like bad idling and your brakes should not function properly.

Reconnect and you should be fine.

 

I'm not sure it go's. any way you can post a picture?

 

the white arrows are for your EVAP system, not the brake booster as mentioned above (i think he was looking at the red circle instead of the white arrows).

if its not hooked up you will get a code and slightly lower mpg and may run slightly rough.

 

Ok I did not see the white arrows, just the big red circle.

As for the white arrows, vikesfan is right

 

Thanks Guys