Have you checked the cam chain adjustment? It will sound like loose valves if it's loose. Check it while the engine sits there idling. You want to see a small amount of in-out movement on the pushrod, maybe 1 to 2mm. No movement means it's set too tight. More than the mentioned amount can cause engine noise very similar to loose valves. You can tighten the adjuster down to see if it eliminates the noise. You can actually tighten it too much, until the the plunger practically stops moving, then back it off until you get the desired amount of in-out movement. That way you know you're set just a little bit looser than too tight.