Received one of these engines used in good condition. There's a shim in the box, is it safe to assume this is the 'break-in' shim?

The mechanical pinch is pretty much gone. Currently mated up with Pavidis 2050 pip...run times are around 8 min. Engine performs fantasic...using 8mm restrictor, going to try the 6.5mm & 70% WOT to see if run times improve.