my motor has a weird issue, and i was wondering if anyone has any experience with something like this:

setup is a d16z6, ob1, in an 89 hatch. only mod is an apexi gt-spec header.

after the swap, the car ran like *** with a stock p28. there was very little power under 2000 rpm and it bogged like crazy. eventually, after driving at low rpms it would throw a code 1 for oxygen sensor (probably from running to rich or i dont even know what).
additionally, the car had a hunting idle when warming up, which i attributed to a faulty iacv.

running out of ideas to fix the bogging issue, a friend suggested trying a different ecu. i tried using a complety virgin p28, with the warranty sticker on it. i tried using an ecu from a non-vtec ob1 sohc motor...p06 or p05 im not sure which. then we tried my friends del sol s ecu chipped with an ls map for his motor (WrongWD on h-t). suddenly, the car ran fine. no bogging under low rpms, free revving, everything except vtec (which was to be expected, its an LS map). so we chipped my p28 that wasnt working before, and put a gsr map on it (so it has vtec, and then lowered rev limits and such for the poor little SOHC ).
now, the car runs fine. there is no more bogging, the searching idle at warm -up is gone, and the car moves pretty well. it smells a little rich, and i have yet to check my new gas mileage, but thats not a big worry of mine.

so my question is:
what could cause what i thought was an internally stock d16z6 to run shitty with a virgin p28 and run fine with a map desinged for a b18?

even if it had some amount of building, would it need that much fuel?
or am i majorly trippin?

 

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