Torque is turning force. As in the turning force of the crank.
Power is torque x speed. Revs is speed.
You can have an engine that has a peak torque of 200lb/ft but peak power of 300bhp, due to it being able to rev to 9k. Think naturally aspirated, oldskool F1, Vtec, superbikes etc.
You can also have an engine that has a peak torque of 400lb/ft but also peak power of 300bhp. The torque produced means that the engine only needs to rev to say 5k to produce 300bhp. Think turbocharged.
Power is a product of torque and engine speed.
Turbocharged cars produce more torque, much earlier in the revs, than a naturally aspirated engine. Forcing the air in (turbocharged), creates a completely different torque curve to a naturally aspirated engine.
Those are the absolute basics.
I'm not entirely sure of your question, but if you're asking why two turbocharged cars with the same peak torque can have such different peak power, it's down to boost. Boost increases the turning force of the crank; boost can be equated to torque.
A small turbo like a k03 can spool quickly but essentially runs out of boost by 4-5k. Boost will peak early, but then drop quickly.
A bigger turbo like a k04 will spool a little later in the rev range but has the ability to sustain that boost up to much higher revs.
So, remembering the 'power = torque x speed' equation, if the small turbo makes sod all boost at 5k, and the big turbo makes lots of boost at 5k, you can say the small turbo makes low torque at high revs, and the big turbo makes high torque at high revs. Therefore, the big turbo car has more power at high revs, ie peak power. This is why you'll see a 2+ k03 car making the same peak torque as a 2+ k04 car, yet the k04 car makes 70bhp more peak power.
It's all about the torque curve, rather than the torque peak.
Try and find some graphs of 2+ k03 cars and compare them to the graphs of 2+ k04 cars. Pretty similar torque curve up to about 4k, but then the k04 keeps boosting where the k03 starts to give up.
So yes, your big turbo car making 550bhp and 400lb/ft makes the same PEAK torque as some 2+ k04 cars. But peak torque means bugger all. Your car will hold that torque (boost) all the way up to 6k. Same analogy as k03 vs k04.
Upping the torque as you put it isn't simply a case of turning up the boost. All the hardware has to be able to facilitate it, and the map has to deliver it safely and properly. So you're right in saying it's the whole package that determines it.
Hope that answers it.
