White spark plug.
I just finished a build yesterday and was just cruising today for about 5 minutes at no more than half throttle. I am at elevation 5,000 feet, and I was running 16:1 (I know most on here disagree with that, but fred at crmachine.com recommended it to me). I didn't do the WOT plug chop because I don't want to run it too hard during break in, but I took off the plug and it was 100% white, which I thought was odd because it was 4 stroking a lot. Any suggestions? The stock NT jet is in there now. Should I lean out the fuel mix?