To my knowledge, which I have researched extensively, the AJS kept the same engine as the AJ37 and didn’t not receive any upgrade in that aspect, however in game the AJS out powers even the Ja37 which shouldn’t happen ever as firstly the Ja37 is lacking in engine power (and many other things) and secondly as stated previously is didn’t receive any upgrade to the engine
As shown in here the detailed upgrades to the AJ
For that reasoning I propose that gaijin take a look at all viggen variants engine power and either provide reasoning for its lack of power or correct it
I can if needed create a follow up post about the issues with the other viggen variants and what it’s missing or is made incorrectly