that's right, the chip would probably only aid fuelling over the standard boost rating on ecu.
you must remember that a bigger displacement engine won't necessarily require more fuel low down nor will it give the same MAP readings as a smaller engine.
check fuel pressure isn't too high, check the injectors are clean and got a good squirt pattern.
check all sensors are working by unplugging them to check, if the CTS one isn't reading then it'll overfuel as if it's cold starting.