Ironincally ive been thinking about putting two pipes on the nova for exactly the same reaosn, NO chance of getting it on track with its current exhaust so was thinking of a Y piece across the back of the car into two silencers with the exit pipes pointing in different directions (one across one back or down)

With regards to the screamer pipe, it wont make any difference to a static test as its closed of course, can effect driveby though, and in that circumstance the twin exhaust will make less of a difference than a static as its measured from further away so more like to hear both anyway.