puffenuf

Borrow a 2.7L 4 cyl runner from my uncle in law and driving around Costa Rica right know. Has had a serious hesitation for pretty well the who trip/the last two weeks. When you first fire up the truck, runs well. Smooth idle. Also when driving is really great. Doesn't accelerate like my 3.4l but that was expected. The hesitation comes after about 30-40 min driving. When you try to accelerate the engine will cut out/total loss of power for about two seconds, then off she goes. After you let her rest for an hour, it works just fine again.
This is what I've done so far....cleaned maf, new air filter, fuel filter, fuel pump, plugs, ignition coils, replace both cats (they were replaced with generics, would that matter?)... The reason I ask is cause along with the hesitation comes a code, P0420, which refers to the cat, which is why I replaced them in the first place.
My next step would be rear o2 sensor unless anyone else has some insight.
Thanks in advance.