I've been sitting back and watching this one a bit.
Dan... listen to the vid again and close your eyes. Clear your mind of other ideas and just listen when he gives it a little rev. I have a thought...but it'* not a nice one.
OP, what does the oil pressure look like after the car if up to temperature and sitting at idle?
I can easily understand some general mechanics saying the things you heard from them. Although the 3800, when you know it as well as some of us do...it'* not known for any of those issues that they said. There are plenty of other motors that commonly have those items though.
That is a lot of gunk and neglect of oil changes inside that motor. My gut says something that I don't want to tell you yet. So let'* talk about lifters and pushrods. Were any of the rockers dry or drier than others when you pulled the parts off? I could understand a lifter gunking up and clogging or a pushrod for that matter. That could cause a misfire and the noise. Which cylinder is the misfire on?
00 Regal GS: All kinds of cool stuff.