Here are the specs of my initial M20B28 engine build.
I started with a standard M20 2.5 that was mostly complete but partially disassembled. A 2.7 crankshaft, connecting rods, and flat-top pistons came with it. The 2.7 rods and pistons are commonly used in turbo builds.
I used the 325i rods and custom Wiseco pistons. I could not use the stock i pistons because they are too tall with the long stroke of the 2.7 crank.
Here are the final specs:
Type: M20B28, SOHC, 12-valve, inline-6, 325i iron block (bored) and 325i aluminum head, port fuel injection
Displacement: 2,758cc / 168cu in.
Camshaft: stock 325i
Compression ratio: 9.5:1
Fuel injectors: 18.25psi @ 3.0 bar
Intake: stock 325i AFM and intake manifold, K&N cone filter
Exhaust: stock 325i exhaust manifolds, stock E21 323i non-cat exhaust
ECU: Bosch 0261200173, custom chip tuning
Power: 190hp (est.)
Torque: 190ft-lbs (est.)