Zach Turner

I had a friend of mine remove the stock intake and exhaust and install an s&b cold air intake and flowmaster american thunder exhaust on my 2015 silverado with the 5.3 and I now have a MAF code being thrown and a rough idle, I found that he installed the MAF sensor backwards. I fixed it but it still has the check engine light on and rough idle. What can I do to fix this? Edit: I looked this morning and I see the exhaust tips are sooted up.