I think you've double counted some released DMUs. For instance, the pair of 142s which were used on the Manchester to Chinley working in the evening peak (which is now a 323 operated Manchester to Hazel Grove) weren't released in the morning peak.
I don't think that's correct, since the 0715 Macclesfield-Piccadilly is now 323-operated, whereas before it was a double pacer. It's not the same 323 as does 1723 Picc-Hazel Grove, but that's only because the diagrams have been shuffled.
Therefore, the use of the GC 180 working and putting the use of the extra 323 in the evening peak release two units in total, not four.
AM: 0715 ex-Macc (gone electric, saving two units); 0659 Huddersfield-Leeds (shortened, saving one unit); 0636 Victoria-Leeds (shortened, saving one unit).
PM: 1723 Picc-Hazel Grove (gone electric, saving two units); 1717 Liverpool-Blackpool (truncated to Preston & gone electric, saving at least one unit, possibly two); 1814 Victoria-Wigan NW (shortened, saving one unit).
Most of the 185s were replaced by 4 car 156s so we've got something like 8 x 156s replacing 4 x 185s.
Weren't more TPE services combined between MIA and PRE prior to the arrival of the 156s? I'm not sure about that one. Anyway, it's currently 9 156s operating on ex-TPE routes, replacing at least 5 185s.
There's also been a new Blackburn-Todmorden-Victoria service,
Yes, I'd forgotten that, so that's 5/6 units accounted for.
strengthening on the Bolton corridor and strengthening on one Mid-Cheshire morning peak service (the Bolton corridor getting more extra carriages in the evening peak) and possibly strengthening on other routes as well.
I can only go by what you say here, but we can only be talking 3/4 units in total, surely?
You also need to note 30m 142s can't directly replace much larger 46m 156s, anymore than a 2 car 156 can directly replace a 3 car 185.
I think that's what this is all about.
Following services will remain as four car but with reduced seating capacity,
07:57 Wigan NW Victoria
08:21 Blackpool North Huddersfield
08:44 Victoria Southport
10:23 Southport Manchester Airport
11:15 Huddersfield Wigan Wallgate
12:03 Manchester Airport Southport
13:45 Wigan Wallgate Stalybridge
14:23 Southport Manchester Airport
15:08 Stalybridge Victoria
16:03 Manchester Airport Southport
16:11 Victoria Stalybridge
16:30 Stalybridge Wigan Wallgate
18:15 Southport Manchester Airport
18:24 Wigan Wallgate Victoria
19:35 Victoria Wigan Wallgate
20:03 Manchester Airport Southport
22:18 Southport Manchester Piccadilly
There are two diagrams jumbled together there, so if each has gone from 156+something to 142+something, then two 142s saved elsewhere have become two 156s saved.
Also EMUs are less flexible than DMUs so there's less efficient diagramming with some units having longer dwell times.
The only serious drop-back remaining involves the Airport service (c.xx.40 into Lime Street, c.xx.15 out). The c.40 minute drop-back at Victoria now only applies off-peak, at peak there's much less slack.
So if we were to suppose that the 319s were really diesel, and could therefore interwork with any four-car diesel diagram, how many units could be saved? One to two, I would guess.
For instance, a 4 car EMU can't split into two at the terminus station with 2 carriages going on to a non-electrified route.
I've already supposed that most of the 319s have replaced 2-car dmus, so I think that point is well covered.