I'm running these http://www.summitracing.com/parts/PYE-MVR10/ behind the 318 in my Dart. I simplified the mess by ordering the whole system w/ X-pipe. The fit is about as good as can be expected from any system-in-a-box and it sounds good. There's no drone or weird resonance under any driving conditions that I've encountered. The system price has gone up a bit from when I bought it, but it's still an excellent value.