A) without a cat and resonator it will sound raspy and junky. these cars make a foul exhaust note, no matter what you do to the exhaust.
B) backpressure doesnt matter on a roots blower car, so dont worry about it.
C) you need more than that stuff to get that pulley on. you need some exhaust mods (the catback does absolutely nothing for performance, so that doesnt count) to help with the flow you just created with a smaller pulley. i suggest getting headers as they are pretty cheap nowadays.
D) get a DHP or an overkill. ZZP is known to have crappy PCMs around here
