how can I make my homelite chainsaw drop revs immediately ?

I have a homelite CSP 3314 saw which I have just replaced carb fuel lines and filter after some time being unused. I now have it running but when releasing the throttle it will not drop revs straight away.It "picks up" well and revs well so I think the carb seems to be set up OK. The replacement carb is a RUIXING 300981002.
(The original was a Walbro WT 673. This saw is the same as a Performance Power PWR33CCCSA. Also looks like a Ryobi RCS 3335.Any help would be appreciated.