Do you know why the other Golf got scrapped? - there is always a reason why they get binned.
Always best to keep all the known good items together - likelihood of troubleshooting is reduced if you know it all worked before. Loom damage can be very hard to find - my old Mk4 had a problem with the throttle body, had a pro auto electrician and a very knowledgeable mate look at it -no one could find the damage. I ended up having to rewire my throttle back to the ECU.
Try swapping the inlet over for your old known good one, if you are still having trouble, you need to swap over your old engine loom.
No idea, the golf I have I bought from the auction, it is a cat n with airbags deployed and a hole in the sump. The engine was running without any oil and probably nearly seized itself so to be on the safe side before I resell the golf, I bought the exact same engine which came with the turbo, alternator, injectors, throttle body, intake manifold, spark plugs, coilpacks.. Pretty much came with everything except the gearbox and I thought it should be a relatively easy engine swap until this stage. I tested the engine a few days ago without the MAF sensor and it ran fine so I thought okay it should be good until yestarday when I got everything on and it was nearly time to celebrate but when connecting the MAF I started getting rough idles/cutting out.
Tbh it could be £550 wasted on an engine as there was no way to test if the engine worked before buying it so the person most likely was selling a dodgy engine to me. Now im stuck with 2 broken engines and £550 out of pocket with this very annoying issue to diagnose!
Cant really seem to think of anything else to try other than swapping the intake manifolds over now and while I am at it, I might as well change the injectors over too. If not that then I really dont know what else it could be? The engine loom seems good as in the connectors etc and im not getting any faults in VCDS other than this intake manifold runner control fault. When moving the actuator by hand, I can hear the flaps moving inside the intake manifold (with a bit of resistance) so im not sure why the error in VCDS. Its telling me the basic settings are not done for the intake manifold but when I try the basic settings instead of "ADP.OK" I am getting "ERROR".