no ipod plug for a lexus

hey guys have a 2003 lexus IS300 with a premium audio system.want to add an ipod module but so far no luck, for some reason this model car is not compatible. the stock radio has a 6disc indash with a tape deck below with no aux. button or no sat. button. there is an open female plug behind the unit that it is not used, I tryed using a perphieal ipod module and plugged it in the female 20 or 12 pin plug, the ipod played but as long as the cd was playing at the same time and there was static noise too. in that unused female plug is there an aux. input that i could hardwire using two rca tips that will work. trying to add ipod and xm. thanks. 

Have you thought about recording an audio CD with blank tracks. You could insert that disk when listening to the Ipod.