Either get a full standalone computer similar to a Motec/Autronic/Link
ecu or a full
ecu reflash simiar to Verso/Ecutek.
Mixing an interceptor with a learning
ecu could be bad in some cases. How can you be sure that the "tune" that it has now will remain for the life of the vehicle?
Take this image example: (stole it from one of intra's previous posts)
Notice something funny?
As boost rises (Yellow Line) , the engine starts pulling timing out throughout the range where you are on boost (Pink line). So from about 3300rpm - 5300rpm (Blueish line) your missing a few degrees here and there.
Now compare that to a proper
ecu or reflash where you have the option
to advance that timing to make more power (and safely). Anyways its your money and your choice , up to you to decide.
Specs on this graph are
Impreza MY01 WRX.
Unichip.
14 - 15 PSI.