'97 4.0 with '92 pooter

[FURACERMAN]

Just curious. My buddy was telling me that his mom had a '97 cherokee with a 4.0, and a 5 speed. I guess it fried the ECU, and the first thing they shop found was a '92 ECU, so they threw that in. I thought all vehicles changed OBD systems around '96-'97 so the earlier model ECUs don't work. But he said it ran, and was actually a bunch faster. I hear the later 4.0s used different manifolds (I don't know whether exhaust, or intake). And I'm assuming that, combined with the less crapped out ECU is helping it produce more power. Any insight?

[rustrtal]

They would have had to do alot of harness changes to use a '92 computer in a '97. Jeep used their own system up to '95 then converted as required to OBD2 in '96 and then changed the XJ all together in '97.

The later years did use a better flowing intake manifold, they are more rounded compared to the earlier years and they also went to aluminum pistons. Not too much other stuff changed.

From the ones that I have owned it seems that the '96 was the quickest to me.