just curious has your local mechanic went through the basics with out using the computer to diagnose it... like Check fuel pressure to isolate it as an ignition problem? Check coil ground...
Check for spark etc...

The computer wont throw a code if the opti is bad actually. And 17 sensors dont go bad at once so its probably taht u need a new computer... Try cleaning out the terminals.. fixed my friends computer problem on his 95.