The extra 25 horsepower comes from additional lift and duration on the intake camshaft, and the necessary fuel mapping programming differences to accompany it. That's it. All other equipment on the engine is exactly the same. Early Northstars (like 1993-1995 engines) had stiffer valve springs on the Touring models, but starting in 1996-1997, all Northstars were equipped with the stiffer springs, so that difference went away.
Increased performance is due to the extra horsepower and the shorter gearing (the Touring models have 3.71:1 final gearing and the "base" models have 3.11:1 final gearing).