The idle screw may be sealed but u can use a ounch or screwdriver or whatever to break threw the seal and adjust it. I bought 85 720 and it idled at 2000rpm. I fixed a few vacuum lines still had same problem.. replaced o2 sensor still no good adjusted the idle screw... the previous owner had already broke through the seal to access the screw. Got it turned down to a smooth 800rpm.. on the bottom side of your hood ahoukd be a sticker twlling what rpm