While breaking in my new rebuilt engine...i checked my plugs...i haven't taken it above 3k but heres what my plugs look like...1- white, with white ash 2-bright white with some ash 3- half kindof black, half white 4-almost all black....i've checked the timing and thats straight..i've tested to see if i could hear the injectors work and they work...i've checked the spark plug gaps and they are straight(they are 2steps colder for my turbo)...my question is what else should I check? Why would one cylinder be running so rich and the others lean or halfway lean..any suggestions on what this could be? thanks

 

try some fuel system cleaner. then look at the plugs.