It would probably be better if everyone stopped calling "the 92 problem" "the 92 problem" since the "problem" isn't limitted to 92 model year cars. "The 92 problem" is what they call it when a standard ttl5v or serial cable interface won't work on an SVX. To my knowledge nobody has identified what the difference is between the cars where a standard ttl5v cable will work and the cars where they won't nor is anyone trying to.
SVX ECUs and genuine Subaru diagnostic equipment, ie a Subaru Select Monitor, do not use a standard ttl5v interface. They use a line driver and clipping circuit to provide rock solid communications. I provide the exact same line driver and clipping circuit in the "ECUtune OBD1 Control Unit to TTL232r interface." This interface has a 6 pin plug on one side to plug into the standard ftdi usb to ttl5v cable and a 4 terminal block on the other side to connect a select monitor harness to. I sell them with the select monitor plug included and already attached (which I purchase from another member here).
This is the correct interface. It works on all SVXs, at all times, perfectly, without messing around trying to adjust a comparator to work around not using the right line driver to begin with. If you aren't using the ECUtune interface you are screwing around with the wrong thing. I bothered to make them so you don't have to do that.
http://www.ecutune.com/ECUtuner.htm
I just had a look at the evoscan website. It looks to me like the evoscan cable is an ftdi usb to ttl5v cable straight to a select monitor plug. So while I'm not suprised this cable isn't working for you the ECUtune interface with an ftdi 232r5v cable should work perfectly with the Evoscan software. Since the evoscan cable doesn't have the 6 pin plug the standard ftdi cable does you'd have to cut it and solder it or something to use that cable or just buy the a standard ftdi cable.