Why is the E250 5.8 weaker than the 1995 E250 5.8?

[E150 4.9 1990]

The 95 has 240HP and 340ft.lbs. The 95 only 210HP and 325ft.lbs. The 95 revs higher. Its peak HP comes at 4200. The 96 only 3600. Only the fuel + ignition map of the vans are different or there are mechanical differences too? Is it possible the get a chip or something which brings the old power? Would it have any disadvantages? I mean worse mpg or whatever. If I am right at 96 there was a system switch, the 96 is already OBDII so a simple ECM unit change doesn't go... I am so curious, how it would drive with a little more aggressive setup!