THANK YOU VERY MUCH! I bought three PT145s based on their fantastic combination of price and features and my excellent experience with three PT1911s. However, after months of struggling, spending money, and trying al sorts of crazy things to correct the nose-diving issue (you got it--Taurus was "unaware"), I was getting ready to throw in the towel, but I'd gotten to the point of suspecting the springs (shouldn't have taken me so long), and then I happened onto your blog.
I immediately purchased ten, tested all ten last weekend, and had ZERO nose-dives in about 250 rounds. I did get a few FTFs, but I blame most of them on the ammo (Speer Gold Dots which SUCK IMHO) and maybe one or two on the feed lip, which leads me to my one other recommendation--use a Dremmel tool to remove material at the feed lip (a nice arc that follows the circumference of the round sitting in the chamber without removing material from the side walls has worked for me) to prevent the edge of the casing from impacting the feed lip during chambering.