I'm not suggesting retarded timing. Peak torque is the indicator that you have a very safe timing curve that will keep an engine alive. If you tune an engine to peak torque, than add timing, you will make more hp at that load point, at the cost of torque and engine longevity. Peak torque indicates a timing curve that is using the energy of flame front to roll the crankshaft forward. If the dyno is showing torque falling off, but hp going up... It tells me that the flame front is happening a bit to soon, creating opposing forces on everything from the headgasket to the main caps and everything in between. Hp goes up with advanced timing because the torque lost to advanced timing gets "stored" in tdc dwell time(high cylinder pressure), and releases in the instant there is any rod/crank angularity after tdc. No problem if you have real strong components...but a very fine line to walk with stock based parts.
Lets say you want a stock based 900hp engine. For discussions sake, say the engine is on the dyno and at 15pounds of boost it's making 875hp at peak tq. You could bump in another 3 or so degrees and get real close to your 900hp goal at the same boost level, OR you could give it a touch more boost and re-tune to peak tq timing.
The first scenario gets you your 900hp with added internal stresses and less tq, with a more fuel efficient engine.
The second scenario gets you the 900hp, added tq and lower internal stresses, with a less fuel efficient engine.