The Ki-84 Hayate was a good plane. Built to replace the Ki-43, the first prototype was built in '43. By the end of '44 1,670 were built. Considering that production started in April of '44, I'd say that is mass production. The numbers I find are that 3,382 aircraft, excluding pre-series and service trials aircraft, were built. I also find that all models were powered by a 2,000 hp Ha-45 (type 4) engine giving it a top speed of 388 mph at just over 21k. Good rook plane

. I'd like to see it added eventually.
Ki-84-I-Ko--2 20mm and 2 12.7mm
Ki-84-I-Otsu--4 20mm and 2 12.7mm
Ki-84-I-Hei--2 30mm and 2 20mm--this plane was a specialized buff interceptor but very few were built
Climb rate was 3,790 ft/min and max range was 1,025 miles.
Please feel free to correct any errors.