Comment on massplumber2008's post
Good Morning Mark,
First thank you for your thorough answer. The "main stack" only has the bathroom sink going into it and then it vent straight up through the roof at that point. I only have one bathroom on the main floor (cape cod), and may tie into the 3" vertical stack for a 2nd floor bathroom in the future. Per your and others suggestions, I am switching over to wyes on the horizontal and the kitchen sink will take another route. The venting seem to be the easiest of all of this. The bathroom sink is not vented since it is 24" from the 3" main and connects via a 3x1.5x3 sanitary t. The shower is 6 feet from the 3" main vent and has it's own 2" vent which connects to the 3" main in the attic.
Thanks,
Rob