I'd still wrap it for two reasons.
Turbo systems work off heat. By allowing the heat to dissipate, even in the downpipe, it is losing efficiency. More importantly, the law of thermal dynamics says that heat will always go to cold, NOT vice versa. So that downpipe and turbine housing WILL heat up your air. And since its all post intercooler, its just heating it up right as it goes into the engine.
Also, Your downpipe looks too small to me. On a PT76GTS and your engine, you should have a 4" downpipe.
My phones on if you need.