99 cougar engine issues
 

I have a 99 cougar 142k auto v6 the car has engine codes p0171 p0174 p0420 it is leaking gas from the intake manifold will upper and lower gaskets fix this? Also I have a SRI on the car and I tried cleaning the maf yesterday and now I get a burning smell and if I rev it up to about 3-4k rpm when I release it kinda back fires or I hear like a pop sound is this the maf bad? Any suggestions will help