Yea it is that one line that is left open. and i am not sure if it is plugged or open. like i said earlier i was stalling constantly and when that line was plugged the car ran. so i have no idea. i know where it goes, i just dont know if its capped off or not

 

The Y is a 3-way joint, as shown in the vacuum diagram I posted in post #6, it does not show it goes to anything else.

This other thread from another user also shows it is unplugged.
https://www.hondaaccordforum.com/for...coupler-50697/

This other thread where you also posted the same question, shows the OP's 3-way joint was found to be unplugged.
https://www.hondaaccordforum.com/for...ections-32472/

Here is another diagram showing the parts to check for leaks related to a code P1456.

 

Thank you!

 

Turns out the line is left open!