If your VRs are OBD 1 then you have an ISV (idle stabilisation valve) its probably that has got a bit dirty... you can remove it and clean it up and it should help... If your VRs are OBD 2 then it wont be that! lol. Other things to look out for with rough idle or start ups is plugs, leads, coilpack (check for cracks) and also the MAF.