Black changing from 100% to 91% when exporting PDF

Hi all - 

As noted, 100% black in ID turns into 91% in a PDF.

This appears to be similar to this post - however, I haven’t found something that works, and am not sure what’s going on.

Have there been any updates to the process here? Any troubleshooting tips?
Maybe export to a different profile?

[edit] Gray Gamma 2.2 seems to be ok - not sure why 100% black would be changing in other export profiles though… ?

FWIW - we’re printing in black only. There’s an RGB image with an almost-black that’s converting properly. 

(I didn’t receive a profile...)

thanks!