Random stalling out???

Hello fellow svx owners,
I hope somebody out there can help me with this problem... its got me baffled. While driving my SVX, it will randomly just stall out. It happens while im sitting idle, it happens sometimes when i take off, it happens other times slowing down.... its even happened at 60 mph. The tachometer will drop very close to 0, hang there for a second, then shut off. It seems to do it more often lately. Ive had the problem since this past november, but it comes and goes. I changed my spark plugs (platnium of course), fuel filter, and air cleaner. These things didnt help. I even tried filling it with a few tanks of 94 octane, and that didnt help. Does anyone have any idea why my SVX is doing this?

any help appreciated