Bill here's a clearer picture. You will notice that neither of the inside edges line up with the ruler but the top one is much lower than the bottom one.

 

The bottom Turbo housing is the housing of choice for the larger PP and in fact they actually remove the insert from the old housing ( if damaged) and put it in a new one if they can't get the housing they want. Could be why they idle so badly, but it certainly breathes better - at the higher RPM.

George,

 The timing on the two housings you have is certainly different. I haven't heard of different timing on turbo housings. The closing event is the one changed from the look of things. It seems strange that they would lengthen the closing on the turbo, as this would cause more overlap on a system with more back pressure. Any chance the second housing might have been ported?

 

Bill - definitely not ported, in factory condition except for housing being scored.

 

 I don't know why everyone is going on about idle. I have worked on bridge-ported RX-2s and that car idled worse than any PP I have ever heard. The only reason that ANY of the racers don't use P ports is that most of the racing organizations prohibit the mod!

 

Just trying to keep overlap to minimum in an effort to minimize the overlap effect with the PP.

George ( down under)