The new Nissan Stagea is equipped with the RB25DET engine, which by default produces less power than the RB26DETT found in the R34 Skyline GT-R also present in the game, but for some reason with all Race parts equipped can make over 100hp more than the more desirable and technically more durable from factory RB26DETT (910hp vs 798hp). Not only that, its Engine Upgrades are pretty unbalanced, because the first available Fuel System upgrade, Sports tier, adds a whopping 25hp to the stock engine, while the same upgrade on the more powerful Skyline GT-R only adds 15hp, and the Race Fuel System adds 23hp - less than the Sports upgrade on the Stagea! This also applies for the RB26DETT (2.6 I6 TT) Engine Swap available for the Stagea, effectively making it entirely useless.
For that reason, I think the Stagea’s RB25DET should recieve Street tier upgrades for all Engine parts that don’t currently have it: Intake, Fuel System, Ignition, Camshafts, Pistons, Turbo, Intercooler and Oil & Cooling. This will allow for more space for upgrades in lower classes, while also not breaking any tunes that have already been created.