borla 8 stack itbs

So I have a few issues going on. this is a 6.0 swap in a 41 zephyr. it has a mild cam stock stall. with borla induction individual throttle bodies. my first problem is there's a fuel trim imbalance from one side to the other. customer stated he calibrated both sides with a airflow reader. with a .2 .3 discrepancy but the amount fuel trims differ is almost 30 percent. one bank hits +17 and the other is hitting -14. my second problem is rpm flare. rpms will shoot up to 1800 coming to a stop in neutral. Ive already messed with throttle follower decay and throttle cracker is set to 0. IAC counts go up to 150 and stay there for a few second until it finally hits 0 mph and a second or 2 later it finally idles down. any insight would be appreciated.