thats what i thought ive messed around that much with it,when its cold its proper noisy the hissing but i cant find anything when its warm the hissing sounds like the charge carrier,ive had the car running and sprayed some brake fluid around all the pipes in the hopes the revs would rise when sucking in the fluid but nothing.is it a nig job to remove the inlet as i would take that off so i can inspect all pipes hoses and idle valve itself which is right down the back