this is from the greddy homepage ...
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10156633 Accord V6 2/4dr 1998-on 60 115 $649.00
10156634 Accord V6 Dual Opt 1998-on 60 115 $439.00
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from my knowledge, you have to get the single pipe, then add on the dual option. i could be wrong though, but i'm pretty sure about this.