You will get fuel out the exhaust and its not much fuel its more oil. You also dont want to do the idle method of break in. You need to run the truck and get it up to temps as quick as you can. You can also lean out the needles just a tad to get things going. After every tank and every cool down make sure you put the piston at BDC. After every tank you can also lean out the needles a little. Once you get about 4-5 tanks tune it and let it rip.

Running too rich is just as bad as running lean.