1985 Factory "2nd design" Hot air intake??

[BLACKHAWK38]

I my GM 44W parts book, I have come across what seams to be 2 part numbers for the hot air intake manifold. The well known 25515925 , and a Unfamilar 25523551 slated "2nd design for engine codes NCB & NDB.

Where as, the 25515925 was for engine codes NCA & NDA, ??

GM parts experts please help

 

[WH1Driver]

I'm interested in this as well. I have engine diagrams photocopied from a GM book that show two different intakes and setups for the turbo. I believe one they specify as 85 and the other is the one I know on my 1984. Anyone know more on this?

 

[SLOW_85]

might be referring to the Riviera hot-air setup.
Same intake different turbo adapter.
Only thing I know of, maybe someone else can chime in?