If it plugs into ECU more than likely superchips, depending on what you want a "195 chip" will give the power in the name needing only the beige injectors you mention none of the rest. Think a fuel pump upgrade may be needed.

If it only smokes on cold start and is fine when up to temp, I would think it's something wrong with the cold start, I.E overfuelling.

Turbo has two pipes one flow and one return, one you mention is the return.

As said ideally you need to take for a setup as well as getting the car running right and safe it can also reveal any bodge work which has been done previously.

Martin