ok well you dont really have anything to worry about...heres what i think :

you have a chipped ecu...where it probably raises the fuel maps,and air maps between 6.5 and 7 k rpm..right past vtec engagement..to supply the engine with more energy..therefore burning more gas...if you have an excessive amount of fuel dumped at one time..you're gonna run rich..causing "black" smoke to come out...i mean im not saying its good to ride around like that..but if i were you..i would get another ECU,that has a simple chip in it..nothing too fancy..throw it on...and see what that does...

if that doesnt work..and it still runs rich at that certain rpm...check your O2 sensor..and other parts related to burning excessive fuel.


and if its just a "little" smoke..then dont worry too much about it..most of the time..running rich on a honda cant be helped..i mean im boosted...and theres almost no way i will "never" see black smoke..or never run rich..as long as you're not flooding your cylinders with fuel..you'll be fine.