Using LP version 0.10.4 build 5 1.12.2
ItemStack Extraction Upgrade just doesnt seem to work. When I put it in one of two slots by module upgrade in chasis pipe, it does nothing - extractor module just continues to pull items 1 by 1 in default period of time.
On the other hand, Item Extraction Upgrade works normally, like when I put in module upgrade slot, extractor module pulls 2 items at once.
Please fix it ASAP. I need it for fast extraction.

You need multiple ItemStack Extraction upgrades just as you need multiple Item Extraction Upgrades. However, it would really help if the tooltip gave any indication as to what the modules actually do.

It seems to work as intended from you description, but the item description should be updated.

Update: I did some testing and it behaves really weird. Instead of taking whole stack of Items, it just takes 1 item from 2 stacks. I dont think its intended behaviour, but if it is, then this is way too slow, because you can have only 2 upgrades in module and there is no 'extraction pipe' or something like that. Even basic 'WOODEN TRANSPORT PIPE' from buildcraft can extract faster than this :D :D

Update2: I found a way of fast extraction, with stacking Item Extraction Upgrades in upgrade slots and using multiple Extraction Modules. But still I think ItemStack Extraction Upgrade is way too weak, when its just upgraded version of Item Extraction Upgrade and basically it does same think, but different way...