I have a 2l duratorq ford s-max mk1 and it drives really good, but anytime you have to move off from stationary it is so weak that if you are uphill you are most likely going to stall unless you rev it to 2-3k rpm. The problem is anytime you give it some gas when moving off and start releasing the clutch it just seems as the computer denies the throtle pedal and rpms drop drastically. That happens only in first gear, moving off without gas and with is almost the same the second you release the clutch and you are not doing it slow enough rpms drop to the point engine almost stalls and it does not matter if any throtle is being applied (unless the rpms are stupidly high like over 3k). Forscan shows 2 unrecognized error codes in pcm and 2 more that are not relevant to this problem, there is ESP malfunction glowing on dashboard but not pressent on forscan dtc's. I have no idea what is causing car to not take throtle pedal when moving off, it seems as the computer is trying to lower it.

Added a few photos for context.

 

 

Update 

After running a BCMii Self-Test while engine was on 2 more errors popped up. P060D and P0222. And I think the ESP malfunction could trying to kill engine rpms when moving off as a measure (just a thought).

I have access to a same year Smax 1.8l and it does move off really smoothly by even increasing rpms by itself to about 1.1k. When I have time I will check what is the MAF sensor reading on this one.

I think that the throttle pedal could be faulty.