Service parts may not always have been tested before shipping from the manufacturer. Many manufacturers do so, per the original specs and requirements, but I've seen enough while I was in the business to know that some will skip expensive testing on service parts.
Remember that companies are required to provide service part support a minimum of ten years, or that'* what it used to be. I believe it may be 15 years now. That means that a maunfacturer must keep all the part specific equipment for all those years. It means a whole boneyard full of obsolete equipment must be kept to do the occasional service order...at original high-production prices
Anyway, sorry for your trouble, but glad you got it done and done right.
Mike: 1997 SE w/ 183K, aka White Horse
, Gutted Airbox w/K&N, drilled 180* t-stat, tint all around, clear corners w/SilverStars, "PONTIAC" light up tail, PEMs, NGK TR55s