I give up

A flashing CEL (Check Engine Light) is something serious to be concerned about. A flashing CEL indicates that your vehicle's engine is misfiring, or worse. From the information you have given it would be very hard to say exactly what is wrong with the vehicle. Guessing and throwing parts at a problem can get very expensive. I would recommend taking it to a repair shop and paying for diagnostic. It could be a number of things at this point. What type of codes is the check engine light giving you? What type of plugs did you install ? Does the vehicle have compression?

Must have *PROPER* > SPARK - FUEL DELEVERY - COMPRESSION - CLEAR EXHAUST PATH .... Which is NOT proper? .. You stated "no mechanic can figure it out" .. Not true!! .. Through systematic *hands-on* testing with the proper equipment and knowledge, this problem shouldn't be that difficult to diagnose, then reach a proven solution for the fix... However that's not possible over the internet... Good luck with it!