What is the cause of a P1472 and P1471 error message? See below for detail. on 2002 Land Rover Freelander

Have a 2002 Freelander HSE with 90,000 miles. The Service Engine light was on and there was a significant decrease in acceleration. Took it to a local mechanic who said that the catalytic converters needed to be replaced. Replaced both including 4 oxygen sensors. Could not clear code P1471 and occasionally P1472. Replaced Mass Airflow Sensor. Code P1471 still would not clear. Removed engine cover, including the intake air filter. Car ran great, no problems. P1471 code cleared and service engine soon light stayed off. Replaced the air filter with a high performance air filter, attached to the Mass Air Flow Sensor. This seemed to solve the problem for approximately 20 miles and then the Service Engine light came back on. What's the problem? Can you help?

by in Richmond, KY on August 16, 2012
1 answer
ANSWER by , October 22, 2014
well an exact answer i cant exactly give, but they have a variable intake system (vis), and the little butterfly flap inside the intake is notorious for getting stuck or faulty actuator motors. might check the linkage by pulling the motors off the back pass of the intake manifold