[mwebb]

first test results show
at 25 mph
semi high HC 112 ppm but also
only 9% co2 with 8% 02 @ 2500 rpm

if the cat was working well expect over 14% co2 and 1% 02
===============
the cat works by combining HC and CO with 02 to form
h20 and C02

your test results show that you have plenty of 02 and HC
but C02 is low at 9%
so the cat was not doing what it is supposed to do

or
it could be dilution , an exhaust leak after the cat but before the tail pipe ,
atmospheric air could be mixing with the exhaust gases
BUT
there was no dilution on your other tests so unless you have an intermittent exhaust leak that only shows up when you exchange the ECM and AFR / 02 sensor .

then
your cat is dead er than dog poop