dlarrivee said to the original poster that if he moved his Wye downstream, to be sure the pipe would be 2" diameter and not 3", upstream of the new Wye.
The thing is, one guy saying to another over the internet, just do this and that should work, isn't always going to be good advice, unless it gets checked and double-checked. Why not just let the "correcting party" have an easy time of it.
Now, listen folks; when someone cuts in to say uh-oh, that's a good time to go silent and wait.
So you are a plumber now?