[JAMF]

So the PTO was the first to receive the J (I suppose due the more needs for long range and safety flying over long sea distance) ...

Well, as General Kenney described the proceedings, in the PTO they were happy with anything they could get their hands on and the ETO had first priority and wanted the P-51 more than they wanted the P-38. That was also before Charles Lindberg got to fly with the boys and learned them how to get more mileage, by using a different way to manage the engine. (Lower revs (prop pitch) at lower throttle and such things). When they arrived in the PTO, they were grounded for quite a bit too, while they fixed some things like installing self-sealing tanks.