I just recently put new engine in my MC is it is running very sluggish and it misses at idle my check engine light is on the codes that are popping up are p0102,p0201, and p0412 any help will be appreciated!!

 

You are having malfunctions in the MAF, the injector circuit for cyl 1 & the secondary air injection valve circuits. My suggestion would be to double check all connections to insure they are all clean/tight. Then clear the codes and see if any come back. If they do then diagnostics of the individual circuits will be required to determine what is setting the code(s).