I recently troubleshot some IACV issues in my 2003 2.5l Outback. I ran into some apparently defective replacements. Here are some notes about what I learned.   Symptoms included stalling at idle, hesitation when shifting, and a P0519 code, all suggestive of a "sticky" IACV. Cleaning the air passages only helped a bit. Replacement IACV are horrendously expensive - $300 from most after-market vendors - so it was worth trying a bit harder to fix the existing unit.     This model IACV consists