I can't understand why class 313 appeared in the GWE route? In GWE addon it replaces part of class 166 services. Class 313 has never been used between Paddington and Reading. Why did DTG make this changes?
When did DTG add the 313 to GWE? I'm not at home right now so I can't check, but I highly doubt they added it because, as you said it doesn't operate there in real life.
To the best of my knowledge the Class 313 is not on GWE. Think the OP is getting their routes/trains mixed up… 313’s have never run on the Western, the only time you might briefly glimpse one is passing over on the North London Line at Acton, but 1. That is not a “live” railway on GWE and 2. When GWE is set, the 378’s had started working NLL services. If anything was going to be added to GWE it would be a reskinned and OHLE operational 387 to simulate the Paddington to Hayes shuttle service, introduced for the Western Electrostar shakedown period.
Check if you have the FGW unlocker mod. I think the initial release of that mod introduced 314 and 313 - maybe by mistake.
Check if you have the Mod that adds the FGW HST and 166. Its main variant adds (most likely a bug) the 313 and 314 to GWE. If you want the FGW HST and 166, but no 313/314, they do have a version that fixes this bug
No 313 on my version of GWE If you have mode on your system then it's likely that rather than the vanilla game.
This. It's an odd consequence of the original version of the FGW Livery Unlocker mod (which was, to be fair, released before Cathcart): 313s/314s start spawning in place of 166s. However, an updated version of the mod has been released which fixes the bug.