?? there is no pipework with the hks defencer, it's an electrical device that you splice into the ecu loom.
but to answer your question, a fcd set up properly is ok but not ideal.
What you are looking at is a cheap way to increase boost but it can be risky if not done properly, i.e, you can run lean and feck engines.
If your looking to increase power on a budget and havn't already done so i'd get a decat downpipe and decent filter.
If you want to increase boost but don't want to spend £££'s on ecu's then get a proper electrical boost controller like an apexi avcr or a scooby ecu chip, keeping boost to around 1.2bar but i would look into ensuring the car gets enough fuel. Ideally on a r/r or someone with a wideband to make sure it's happy with the extra boost.
Johnny