Re: Noisey hydraulic tensioner V6.
I don't know if this is the same tensioner fitted to the old 12 valve 3 litre V6 engines but if so, mine did it too. It's actually not a tensioner, it's a DE-tensioner! I couldn't believe this when I was first told but sure enough, as you rev it up, it SLACKENS the belt! The way it was explained to me, the biggest load on the belt (and therefore the biggest chance of it slipping) are when the engine first fires. It goes from a a few dozen RPM to 1000 in a fraction of a second. As the revs rise, the tensioner reduces the belt tension.
Anyway, I had the rattling and got so fed up, that I just put a tack weld on the tensioner arm (so it's now like a rigid tensioner). That shut it up! It's been like that for well over 50,000 miles with no problems. When I was told about how the tensioner works, I was also told that I had the belt slighly too tight. Obviously, I don't have the rattling problem now but you could try slackening your tensioner off a bit and see if that shuts it up. Rebuilding the thing (replacing all the seals) didn't shut it up either, by the way!
Also, don't be fooled into thinking your oil pressure is stable just because you have a mechanical gauge! My (electric) gauge pointer bounces all over the place at certain engine speeds. Like you, the first thing I did was put a mechanical gauge on a long piece of tube and taped it to the wiper arm. I then went for a drive and the gauge was stable. I therefore believed that the fault was with the electrical gauge. It wasn't until a long time later that I had a suspected fault with the oil pressure light switch and screwed the mechanical gauge straight into the head (where the light switch goes) with no pipe feeding it. Amazingly, it bounced about just like the electrical one! I concluded that it was the cold, viscous oil in the pipe that had damped the gauge's movement and that my oil pressure DOES, indeed, fluctuate wildly at certain engine speeds!
I don't know WHY it does that but it's done it for at least 100,000 miles now and I don't care any more!