Need dual mufflers, right in front of the rear end. Flat, standard size that the car is made for. Add a transverse to that if you want, but not sure why anyone would want three mufflers. Lots do it, but its beyond me as to why.

Must have an X or H flow Cross in the system for real exhaust balance. I've researched that X is better for flow. Others will disagree.

2.5 inch mandrel-bent tubes all the way from the collectors to the exhaust tips, nothing less Bjorn!!