My 2012 Sentra base model 2.0 was running absolutely fine, but it was throwing a misfire code. I decided to start from the bottom up to see if I could fix the issue. I replaced the spark plugs thinking it might help. I replaced the intake manifold gasket while I was at it. Started my car and now it’s is missing HORRIBLY! Took everything back apart to make sure I didn’t miss anything, put it all back together and it still is missing HORRIBLY! What might I have done to cause this problem to get worse rather than better?