P38 v8 plenum

Hey I'm a newbie here I've recently done my rocker covers after I did em few yrs ago and iv done nothing different but this time my p38 v8 idles at 2k revs but i did notice a bit of gunk in the entrance to the plenum but i didnt mess or clean it....maybe I haven' sealed plenum right or icv has decided to play up help or advice is needed many thanks

Hey there, I would indeed investigate the icv, it could be stuck open! Might just be general crap! Try cleaning it off the bus if you can?