The smaller the capacity of an engine, the easier it is to get a high specific output.  100bhp+ from a 900cc engine is nothing and pretty common in bike engines which often have specific outputs much higher than 100bhp per litre.  I don't know which Daihatsu engine you're referring to but it was probably a motorbike type engine.  Very high revving and almost no torque.

There are still very few normally aspirated road car engines with 100bhp/litre or more. The ones I know of are:

- McLaren F1 V12 (basically two BMW M3 engines bolted together)

- BMW M3 (current and previous model)

- new BMW M5

- Honda S2000

- Ferrari 360

- maybe the new Lambo and the odd Porsche, not sure.

Of those, only the BMW engines have a good deal of low down torque, the others are just race tuned screamers

Michael.