I installed an HKS Twin Power in my car a couple of days ago. Can't really tell but it seems that response above 6500 rpm appears to be stronger. The strange part is, my car shakes at idle and my O2 sensor shows that the car is running rich at idle. I changed the injector map from 1.215 to 1.1 and the car idles right at stoichiometric.

Reverting back to stock ignition shows the normally very lean idle.

Can anyone explain this?

MODS:
PFC, DATALOGIT, M2 LARGE, K/N CONE FILTER, DP, PFS CATBACK, HKS TWIN POWER, CF CLUTCH, B/M QUIK SHIFTER, DENSO FUEL PUMP, NEW 550/850 INJECTORS