egine cuts off while driving

I have a well maintained 92 svx with about 95,000 miles. Lately, the
engine cuts off without warning even while driving on the highway at
70 mph. I've taken it to the dealer 3 times and my local mechanic
twice. They both say it is some type of intermittent problem which
does not show up on the computer dianostic. The local mechanic says
that a selenoid(sp?) on the transmission needs replacing at a cost of
at least $2,000 and that if he does replace it there is no guarantee
that the problem will be fixed. The dealer wants to replace seals
etc. and the transmission but again won't guarantee that that will
fix the problem of the engine stopping while I'm driving the car. I
talked to Subaru of America and was told to consult one of my local
dealers. I've had substantial contact with 4 of the local dealers
here in the Chicago area and none of them seem interested in trying
to help me fix the car. Has anyone encountered this problem, and, if
so, what is the solution. In the alternative, I am open to
suggestions as I really want to keep the car. Any suggestions will
be appreciated!