Short of having a n air-fuel ratio gage, a better method is driving the car and pulling a long hill at road speed. Pull off the road and shut the engine down immediately and pull a plug. "perfectly white on the porcelain" is not what you want.
- EM
I like perfectly white way better than black or oily and brown
OP, what brand a nd heat range, part number, on the plug are your spark plugs? Can you post a picture of one of your plugs on here? If so that will help a bunch on giving you good information
Let us know, maybe a colder plug will help on the color on your plugs
