But it is true... look at the TurboXS downpipe pic I posted. The top part that connects to the back of your turbo with five bolts is an oval-shaped piece that's 4" wide. The actual pipe that's connected to that cast piece is a 3" pipe stretched slightly so it'll make a smooth transition. The piping itself is not 4".
Also, this is taken directly from TurboXS.com:
"The TXS downpipe is larger than any other WRX/Sti/FXT downpipe on the market. Why is that important? Because, despite what your girlfriend might tell you, size does matter. Turbochargers work best when there is large pressure and temperature differential across the turbine wheel. Having a large, free flowing downpipe is what give you that large pressure and temperature differential. The downpipe has a 4 inch cast bell mouth which tapers to 3 inch towards the flange end."
TurboXS's claim of having the largest downpipe on the market is not entirely true though... APS uses 3.5" piping after their cast section, so technically theirs is bigger.
07 WRX (Albins 5MT + Blouch 20G)
Jorge Carrillo Tuned (365 whp/340 wtq)