2006 Z4 3.0si - DSP or not???

I am wanting to install a USA-Spec PA12 Ipod interface in my Z4 with Business radio. However, I am having a difficult time determining whether or not I need the DSP version or not. There is no DSP button on the face of the radio but if I scroll through the mode button there is a couple of DSP choices. I have read on several threads that I am ok with the non-DSP model, but I still am not sure. By the way, my Z4 has a build date of June 2006 if that matters. Anyone out there that has installed this device have some insight?

Thanks in advance,

Jerry

I went ahead and ordered the non-DSP version as I really didn't think that I had the DSP model even though the mode button showed a couple of DSP settings. To be sure before ordering, I looked at the amp and verified that it only had two ports coming from it and no coaxial output. I hooked up the USA-Spec last night in about 20 minutes...I had already located and pried/pulled/coerced the six pin out from under the middle console. The only issue I had was with my iPhone 5. I purchased a clone 8 pin to 30 pin adapter off of ebay. After some googling, i found that for some reason only the authentic Apple adapter works with the USA-Spec. Off to Target I went, plugged the adapter in while in the parking lot and here came the music. It sounds great! The PA-12 is a great unit!