Two issues:

1) I am wondering what a leaking exhaust manifold might look like, if you could see the leak where it is cracked? My turbo manifold (Garrett T3) shows a whitish ring around the lower part of the "U" betweeen the first and second exhaust ports. Could this be a leak from a crack there?

Looks like these rings on this guy's manifold:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2470492148&category=33632#ebayphotohosting

2) Engine has developed a loud, metallic "ringing" sound at easy throttle -- about 1,000 RPM's somewhere near the alternator/AC compressor on the driver's side. Don't get it at idle, nor at higher revs. Only as revs pass up/down through this level. I can also hold the throttle there to produce it.

I thought it was a dry bearing in the alternator, so, I had the best shop in town replace the bearings. But the sound persisted, so I next thought it might be the timing belt tensioner. (The AC compressor is unplugged, so it is not that). Belts are worn, but were not slipping.

Unfortunately, after I loosened the tensioner, I bumped the starter and the belt jumped off, so, I can't re-test for a bad tensioner. It doesn't feel rough, but with 122000 miles on the car and this item of unknown history, I'll just replace it along with the timing belt and front seals.

But I wonder....

What does a "spun" crankshaft bearing sound like, if you can detect it that way in the first place?
--
'Can't understand why people abort Volvos, either'