A high flow quasi-dual is probably the best way to go. A true dual is pretty useless on a 2.5 litre v6, the loss of backpressure would be counterproductive, you would end up loosing tq most likely.

2001 VW Golf GLS 1.8 Turbo
220hp/260tq
Porsche Cup 3s rims w/225 45 17 tires
Oettinger Grille, Votex Rear Spoiler, and way more mods