Downpipe - Mid Pipe (second cat pipe) - Centre - Backbox

I need to replace this (bolded) on my 2005 STi. From what I understand, this section is decat from the factory on STi's (maybe just PPP ones?) but I know mine is cat-less.

Still, it needs replacing with another catless one - needs to be 2.5" to fit my system, any recommendations?

Are the various pipes from various manufacturers all cross-compatible? For example will any old generic pipe fit in between my PPP sports downpipe and a scoobyworld centre - or am I better off getting the scoobyworld midpipe to assure a good fit?

Finally - are there any sensors plugged into this pipe? I'm pretty sure I remember my downpipe to be sensorless so I'm guessing I need a mid pipe with the relevant connection(s)?

Cheers!