Hey dude, very clean spec.
1. The sludge could be cause from your intake, do you wait at least 24 after you oil the filter, before using it (putting it on your car and driving your car). If not you should start doing that.
2. It's somewhat normal though, especially with an aftermarket cai, filter allows more flow because it's not as restricted as normal filter.
3. You can clean in using combustion chamber cleaner. I bought from a Dodge dealership it was like $6. Comes with instructions. You're gonna get a misfire code after you used the ccc (combustion chamber cleaner). Just get it erased and it wont bother you again.
Hopefully this helped man.
K and N Typhoon CAI, Greddy EVO2 catback exhaust, Tein S-Tech lowering springs, EBC Slotted rotors, EBC Red stuff brake pads, and B15SENTRA.NET stickers