If the  Fuel Pressure Regulator wasn't regulating the pressure what would the affect be?? 

The fuel pressure will be to low or to high, depending on whats wrong with the FPR.
..........to lean or to rich fuel mix would be the result.

Ovepressure (more than 2,5 bar) black spark electrode

You will also get black smoke out of the exhaust, when you crack open the throttle heavy. Is it doing this when on the centre stand. I use a cheap 100 PSI fuel pressure gauge teed into the return line. Auto supply shops will have everything you need but make sure you clamp  all the connection with injector hose clamps. Should not cost you more than $20.00 for the whole set up.
Regards Martin.