According to my (infinatly) definitive P38 book (Warren M. Bodie, ISBN 0-9629359-5-6) the numbers with WEP for the P-38J-10-L0 (AC42-67896) which was tested in Dec 10, 1943 are:
MAX SL speed: 345
MAX crit alt speed: 421.5 @ 25,800
Rate of Climb (SL): 4,000 fpm
Rate of Climb (crit alt): 2,900 fpm @ 23,400
Time to crit alt: 6.19 min (23,400)
Service Ceiling: 40,000
I don't see anything wrong with HTC's data.