if the N1K1 was perked for a brief time?
The C-Hog was once unperked but then perked after it reached epidemic status.
*pedantic*We've never had an N1K1 in AH.
The Ta 152H (until late 2006) and the Spitfire 14 (until mid 2013) are the only planes that once had been perked and are not anymore.
P-47N
Pretty sure it was back somewhere from 2006 - 2010. Maybe it was just set at 5.0 ENY. Seem to remember a fuss about unperking/raising ENY value.