Hi all , can anyone help with an issue I have. I own a 2002 wrx sti Impreza, when revs get to just above 2000rpm they jump to 2500rpm an stick there, I can get the revs to go higher but not come down unless I under hear the car then they idle normally again. The blow off valve works intermittently too. I’ve removed they blow off valve , intercooler and pipe work to check for leaks to no avail. Any ideas??