E21 m20 swap help

[Fresco34]

So I have an e21 that was m20b27 swapped by a previous owner. I originally thought the engine had the 885 head on it, cause that was what I was told, but since I'm a dingus after investigation, the engine actually has the 200, since it has the 2.7ETA stamp between cylinders 4/5. Now where I'm confused is the fact that the engine rev's out much higher than the b27eta should (6,200) and has the b25 intake, manifold, b25 ecu and other parts. I know that you can swap all of this stuff over, but still I'm wondering if anyone knows what had to of been done to the engine to achieve this or if it was just as simple as swapping everything over and running it with the b25 ecu.

[hotdish]

It's as simple as swapping it over. I swapped my e30 m20b23 to 325i EFI since L-jetronic parts were expensive to get. You might have more risk of floating the valves at high RPM if it still has the 200 valve springs.