Do I have the wrong idle tensioner?

[Go Metric]

I have negative pressure at the oil cap while the engine is running, using the highly scientific rubber glove test, does that mean my pcv isn't totally clogged, at least not yet?

[vtl]

On a turbo engine PCV has 2 circuits. You need to rev engine above 2500 RPMs and see if the pressure is still negative.

[abscate]

Take it up to 2500 rpm slowly and keep an eye on the glove as a good PCV will suck it into the valve train and leave you with a real mess

[Go Metric]

Just to follow up on this, my replacement tensioner is working fine, though my old one was probably fine except for the pulley having grooves worn in it.

It turns out the clacking noise I was chasing down was actually the alternator, which was not the original Volvo or Bosch alternator. I had used a long handled screwdriver listen to each accessory when I was trying to track down the problem, and the alternator hadn't sounded like the problem at that time, but it was definitely it. The alternator stopped working, and once it was replaced the sound was gone.