My OBXT recently went through a turbo replacement and uppipe swap, and has about 142k miles on it. The new turbo has about 1200 miles on it, and I haven't had any issues with it to date. So, recently I was driving up a hill and as I got into boost I heard a rather loud grinding/rattling noise. It seems to be coming from the center, front of the car, slightly left from center, and is dramatically more prominent in the cold. I pulled the downpipe to see if my new turbo had failed and it was just as good as the day it came in the box. Not an iota of play. What could be going on? All fluids are topped off and I've been religious about maintenance. The trans and diff fluids aren't due for another 20k, so I'm confident that's fine. And to think the turbo swap would be the last work I'd be doing for a while!