I built 1 that made 250ish bhp, but it wasnt easy and it definately wasnt cheap,
They're not realy bad old engines,
But if your looking for decent numbers then its best to start with something else IMO
The only reason i built that 1 was because it was for a formula 2000 open wheeled race car, and needed to run either that or a pinto for the race series, and we decided to go down the i4 route
But i think we ended up with over £10k in the engine all in