I think this is called clocking... need to rotate the compressor slightly from its position where it is mounted to the turbine. How difficult is this "on car"?

I am fabricating custom tubing and am trying to eliminate this ~12° angle-


Here are two shots of a spare- Can I loosen the big bolts and simply rotate it?



THX

 

the correct way would be to loosen the snap ring and turn just the compressor housing, but due to access on the car, i'd say just do as you said and loosen the clamp bolts for the backhousing and rotate the center section with the front.