piston slap/lifter/exhaust manifold

hi. It 'appears' that since an oil and filter change ive developed an engine noise. Its like a tick. Its silent on initial cold start, then after about 30 to 60 seconds the noise starts at idle and lasts about 3 or 4 mins but the noise disappears completley once the engine starts to get up to temprature. Removing an ht lead from the dizzy cap shows 'possibly' a reduction in the noise. But its certainly still there and the others give no change at all. Removing the filler cap, no change or clues. Applying the brake whilst loading it slightly, i could still hear the noise. Im not sure if it increases with rpm as its kinda hard to make out with the increase in engine sound, but it certainly doesnt go away. Ive had a go with a stethoscope and hose on the block, manifolds, tranny, t/case, sumps, exhaust, cat, engine mounts, head, valve cover etc etc and everything of the belt, but cant tie down exactly where its coming from. The only other thing i can say about the noise is in my opinion, its metallic. like spoons chattering. Ive since gone back to the original oil and a new mopar filter but no change. Engine runs fine with no issues. Pressure is good. Are there any other things i can try that will help tie down what/where the problem is before i start thinking about mmo etc.

I think they all make noise. The unusual thing about yours is that it goes away in 4 minutes.