You might try adding a quart of...
Marvel Mystery Oil, to free up any gunk and get it caught in your filter. I dont know how it acts with synthetic oil though, so you might want a second opinion.
You only want to do this if you arent reading full on your dipstick. You dont want to overfill your crankcase. Ask around, and ask how it does with synthetic, unless you plan to change that crossover pipe.
It should only be a few dollars at walmart or autozone. Depending on where you are reading on your dipstick, you can choose between the 16 oz and the 32 oz.