I have an 03WRX that had a Prodrive backbox and H&S de res centre and decat centre. I have since fitted a slip jointed heat wrapped up pipe and a prodrive sport cat down pipe. Since fitting these 2 items it has become noticeably louder and I can hear a bit of turbo whistle and a few pops on the overrun. Is this normal. I am concerned that it may have a leak somewhere, or does the standard up and downpipes silence it that much. It doesn't sound like it is blowing though.
Also with just the sport cat downpipe and PPP back box am I better putting the resonated centre section back in.

 

Mate, I suspect you probably need a remap.