[alfadak]

All of the plugs should be that nice brown color. The SPICA does NOT have to run rich to run right. If your mechanic is telling you that, find a new one. If you are in a place that doesn't have experience with SPICA buy Wes Ingrams book and follow it as the one true light. There is a reason he is considered the guru of SPICA!
In my experience the bosch plugs start turning that color if you are burning oil. This is usually from the valve seals. I think that the factory ones are made of paper mache or something
If the oil consumption has picked up, this might be the case. However, before I went chasing that rainbow, I would get a hold of a manometer or other airflow gauge and make sure that the SPICA is all pulling the same amount of air.
Next, try a different type of plug. I have had good experience with the NGK BP7ES, but everybody has a favorite.
If the problem still persists, you will probably reach a point where you will have to decide how far you want to go......
Good Luck

 

[alfadak]

Manometers are only to be used at idle!!! If you rev the engine at all the mercury will be sucked out of the tubes and you will be very sad
Most motorcycle shops have these, or you could use an airflow meter like a Unisyn (IAP has them) or even better, a motometer ( http://www.racetep.com/weberX.html#websynch). Although $45 is a bunch to shell out for a tool you will use once, there is no better way to be SURE that airflow is even.

 

[alfadak]

Sorry for the double post. I was reading the reply and it occured to me that I haven't asked if the car has sat for an extended period? If so, the seals may have dried or "acquired" flat spots. Sometimes it is good to put some marvel mystery oil in the crankcase and about a teaspoon in the cylinder via the sparkplug well (after the removal of the plug of course) to help condition the seals and gaskets after an extended period of inactivity

Also, if the rebuild was not sanitary or done with care, the car could easily be burning oil. However, as I said earlier the oil consumption should be one of the last causes to be investigated after all others are ruled out.

Be methodical and look at each system. Have you checked the plug wire resistance to make sure they are all the same? Checked the cap for pits in the #2-3 terminals? Plug gap? Done a compression test? (If you have any doubt about the rebuild that would be a good place to start) I also agree that the stock airbox is the way to go if you still have it. You are losing power and economy with the lack of a cold air snorkel (even if it sounds good).

Hope this helps!