Our Crossfires do not have variable speed wipers but are speed sensitive. Having said that, I owned a '94 850 Volvo at one time and it too didn't have variable speed wipers. On a Volvo users forum it was reported that a wiper relay sold by Volkswagen would fit in the relay box and provide the desired vari-speed. It worked like this; turn the wipers on and then off. The next time you turned the wipers on, it remembered the time duration and would continue at that speed until changed. I did this modification to my 850 and it worked like a charm. Neat feature.
Anyone ever heard or know about something similar for our Crossfires?