I only got about 25hrs on my A1A before having to overhaul it (http://www.vansairforce.com/community/showthread.php?t=60675), but in the process I learned there is an AD on the oil pump requiring replacement of the aluminum gear with a steel one due to the potential for excessive wear (mine had not been done). I don't know enough to say whether that not being done could affect oil pressure, but it might be worth checking.
