The guy that recently looked at it said to put the stock intake box back on and that may or may not fix the check engine light. He has been the service manager at my uncles Nissan Dealership for 25 years and is really knowledgable. Unfortunately I don't have the stock one around anymore and cant find it online anywhere, and there are no junkyards around that have a pathy. I currently have a short ram intake which in my opinion would not cause the p0400 code.