Things like good turbo manifolds, intake manifolds, port and polish work, cams. Basicly making the engine more efficient without increasing boost pressure. The more power you can make on lower boost pressures is basicly how efficient your engine is. Turbo sizing also plays a part in this. Using a larger turbine housing with a good size compressor will result in alot better topend without the risk of detonation. You will lose power down low but you can still achieve good power by 4800 or so and hold that to say 8k or 9k depending on what head your running and whats done to the head. (ie springs and retainers and cams)
Its all about efficiency. The more efficient the engine the less need for race fuel as there is alot less chance of detonation as long as your a/f is kept good.