P0171 and P0174

[Z_ealot]

Hey everyone, so to get to it as the title reads i have had 2 codes theown aince getting my transmission swapped out. Im thinking maybe i have an exhaust leak, but i took it back to the shop that did the work which was corner 3 garage and they couldnt detect any exhaust leaks. I have also noticed every so often i will get a slight lag between the time i hit the gas at around 3,000rpm and when the power actually reaches the tires. Also a few minutes after the codes came up the idle of the car went up to about 1100rpm and stayed there. I cleared the codes and the idle went back to normal, but the lag is still present. Just an fyi, the exhaust and air intake are completely stock