Intermittent MAF code but car runs fine
 

The "!" light on my '91 964 C2 comes on everytime I start the car. I have an engine code indicating a 1221, which I understand to be an intermittent MAF code. Anyone know what this MAF code means and if there's anything I can do (besides replacing the MAF itself)? While I had the MAF off the car I noted that there didn't seem to be any way to open the black electronics unit attached to it.

P.S. I removed and cleaned the MAF and the connectors last month while trying to diagnose an idling problem, but the issue turned out to be a faulty ICV. The car now runs fine and there are no idle issues.