So you're saying they were not withdrawn from the ETO, but transferred to the MTO... Select choice of words there Widewing. 
The 9th in the MTO generally operated at lower altitudes than the 8th, and thus the P-38 could operate there more effectively.
No wonder. The Luftwaffe could just ignore them for most of the war.
The Thunderbolt ended the war in the Mustang's shadow, and did not get to go to Korea with the Mustang and Corsair. Unlike the Mustang, Spitfire, and ironically even the 109, production of the Thunderbolt was halted at war's end.
Argh.... The 9th AF
was in the ETO... They provided fighter cover for 9th AF medium bombers as well as tactical air support for ground ops. They engaged the Luftwaffe with great frequency.
In the MTO, 15th AF B-17s and B-24s flew at the same altitudes as in the ETO (see the report below). The fighters didn't fly lower. Indeed, Gen. Twining refused to follow Doolittle's example and insisted on the fighters flying close escort, surrendering tactical advantage. P-38s flew escort until the end of 1944 (at least), long after the 8th had sent their P-38s to the 9th AF (which flew out of Britain, and later operated from bases on the continent).
As to when the P-47 ceased production.... The Last N models were delivered in December of 1945, about the same time the last P-51D was delivered. P-51H deliveries ended in 1946. Both companies saw contracts cancelled, and both were gearing up for the manufacture of jet fighters.
As to the speed of the 109G-6/AS...
Performance of the Me 109 G with DB 605 AS.
Test Report Nr. 109 20 L43
Date 22.1.44
Copy 4
Dept. Flight Testing
Group Performance
1.) Speed at sea level: 315 mph
2.) Speed at FTH: 406 mph
3.) Full throttle height: 27,231 ft.
And this:
