Duals on a 4 banger, Well you will lose torque, and add more weight, but you will add more top end horses. By the time you get to top end to see those horses. The cops will have already caught you. Free trip to county lock up for going over 100.

Now so much for the speech. A nice single exhaust would be a Apexi WS although it is kinda large, but sounds good. Greddy evo is a good one. Tanabe hyper medallion is a good exhaust. All these are pretty quite with a nice low sound. You really didn't say what sound you were looking for.

Intakes. I'd look in the for sale section and see if you can pick something up cheap.