Just a quick question, after you installed the FMIC and the Exhaust, has the ECU been reset?
The stock ECU's can "learn" the way your engine runs and adjusts maps to suit.
Disconnect your negitive battery terminal, put your foot on the brake pedal to clear any residual electricity from the system... (maybe wait 30 minutes as well?...)
Then reconnect it, let us know how it idles directly after the first startup... and then drive it to work the next day and it'll keep getting better and better until it thinks its running well.
This has helped me a few times when I did minor mods to skylines and the "tune" wasn't 100%.