Im hoping to find someone that has infomation or may have used a Sun Interrrogator 1805 tester. I found one in an old garage service station and ended up bringing it home. It uses 3.5 floppy disc to run. I looks as though each year in the 80's had its own disc. There are GM dics 80-88, chrysler 81-87 and ford 81-90. It also has other discs however I did not find one that was a generic that would allow me to use it on anything so I could set timing, check exhaust for carb adjusting and use the scope to see each firing cylinder. I basically bought this for my dad who used a sun machine but his was an analog machine and this one is computer operated. Let me know what you know! Thanks Rod