I would appreciate opinions on what you think is a reasonable gap tolerance for these units in relation to the sides of the housing, and whether or not any misalignment of the two pieces (top & bottom) is acceptable. Thanks.

 

It looks to me like your sections aren't properly aligned together. The side pieces are actually separate and fasten to the PCM frame. I've had the side trim pieces off, but I haven't needed to remove my PCM unit yet like others here have done. I expect that the PCM could be partially or fully removed and the sections re-aligned better.

 

Mine looks very similar except the left side is off by perhaps .5 mm at the most,--the right side is even. I have been into my PCM previously to install the TOOKI unit and found everything just comes back together well.