Originally Posted by Boosted Performance

Jwick, it is not that. For whatever reason a one customer was sent the wrong turbine housing. The down pipe now has a 1/4" lip (3" diameter pipe) past the V-band on the turbine side. This allows for a tongue and groove connection, eliminates the need for RTV, and does not mess with the wideband sensor readings...a much better seal.

So the housing that was sent with that turbo did not have the 3.05" inside diameter outlet flange to allow for the the protruding piece to go in to.