This afternoon I removed my airbox, with the goal of replacing my heater core, and siezed blower. When I got it out and opened up, I found lots more in there than just deteriorated foam seals and dirt. The heater core had been relaced sometime before I bought it. That feels like good news. I have clips for re-assembly! But one of the puzzling items I found inside is a large plate that blocks off airflow thru about 2/3 of the heater core. It is perforated with one row of ~1/4" holes along the bottom edge, and three staggered rows of ~1/4" holes across the top edge. Is this normal? it was sealed in, against the core, as if it belonged there, but I have never heard mention of it. (And I am one of those goofs who reads the Bentley for fun, just to see what is in it, and what I will be in for, when a job comes due.)

  Any clues? My heater never seemed very strong, maybe this is why? The only clues in the archives were some unanswered questions about this same item, from 2006, in an airbox transplant of a 1985 into an '80.