They all just suggestions really. As far as a T vs a Y pipe, the stock one is a T as is the intake for the SL55 setup and that supposedly works as well as the Needswings setup. Remember the air is being drawn into the intake, not pumped.

I did find these HDPE 3" Tee's that could be cut down to fit.
Butt Fusion Tee 3" IPS, DR17 - Hdpe Supply


The OD on that Tee is 3 1/2". And yes, "Butt Fusion" does sound painful.

It could be cut down on each end leaving 1/2 - 3/4" to clamp a silicone coupler or elbow etc. to it. Or it might work just fine as is.
On the center leg that could be cut flush to the 4" OD and a 4" to 3 1/2" reducer could be used to attach it to the TB. That would make the overall depth about 4 1/2 to 4 3/4".



Which should fit within the space between the firewall and TB. I haven't pulled the intake off of mine yet to measure the TB OD. It roughly measures close to 3 1/2"

These are all just ideas I'm looking at. Will it work? Only one way to find out.