Ludwig van has no clue what he's talking about. Oil sludge doesn't even touch the air intake! If you made a cold air intake for your car, there's no problem; there's no part you could hurt by doing that. I hope you don't fall for the things Ludwig van said to sound smart. I mean, think about it. How could oil sludge affect the engine because of something you changed that has absolutely NOTHING to do with the oiling system. Think about that before you choose the best answer.
By the way; if you do have a problem with oil sludge, buy some Royal Purple® motor oil. I would suggest, however, using it before you have a problem. They've already tested it many times before, and it's great at preventing sludge. Before you compromise your cold air intake for some stupid problem caused by cheap oil, I think you should consider using this oil. It costs a little more than average motor oil, but you'll spend a lot less buying this than repairing your engine. Good luck.