To clear up 300HP on the 2.5L
The 2.5L (from what I have seen, I have completely dissasembled my bock) is probably the strongest of the NA 3 engines. The connecting rods are almost exact in design and size as the DISI Mazdaspeed engine. The difference being only the Piston wrist pin size, and that the 2.5L is 1.25mm longer(hardly noticable). It is shorter than the 2.3L na (which has the longest weakest rods).
The cylinder walls are also thick, and the piston design is great and lightweight. The crank is dual counterweight/forged just like the Mazdaspeed 3, and the 2.5L has without a doubt the best flowing head of any of the engines. The intake ports are literally huge and stock ported quite well. Exhaust ports are similar to any of the engines, along with exhaust valve size. Just an intake, header, and tune raising the rev limiter to 7200 (safe on the 2.5L) has been shown to put out aroudn 185-190WHP. The 2.5L continues to make power straight to redline