An ECU shouldn't be hard to find. You will also need a larger radiator, distributor, plug wires, airbox, and little stuff like that if they aren't with it.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>