VQ35 Engine Rattle (Like Tappet noise..) Not Pinking below 2000 RPM
 

Afternoon All. I have rebuilt this engine 1500km ago. New timing chain, water pump, Rings, Oil pump & valves re cut.
Car has just started making a tappet type noise which goes away above 2000 rpm.

I have removed the engine and taken the timing chain off.
The VT cam gears on both Inlet have no play. ( I did read here that this may have been the issue)

There does not seem to be any visable issues that I can see.

Can anybody offer any guide as to what to look for?

The car started making this noise on the last trip. I had to drive it back home 300km where fuel economy and power where unafected. Noise only came back when slowing down and idling through town at 60 km/hr.