It sounds like a tapping or rattling of something metallic to me. If it is getting louder, then something must be loosening or continuing to break.
Try checking these things:
- Engine fan catching on something
- V-belt tensioners are loose
- Perceptible radial or axial play in any of the things driven by the V-belts (checked with belts off)
When you changed the chain guides, did you do the long one on the driver's side, and when you did it did you replace the old metal+rubber one with the newer plastic+rubber one? The old one used a 40mm M6 bolt, and the new style one uses a 45mm bolt, and sometimes if you reuse the old one it will strip out of the head and rattle against the upper timing cover.