Wow that $hit is stupid. I'd probably just ask for a refund. But if I really want to keep it, I would find a competent shop to cut that stupid flange out and weld in a new open pipe piece to make it like the old version. I would also contact HKS to inform them of the terrible design and the hassle gone through and asked for them to pay for part of the work done (not greedy, just like $50-100 depending on what it cost me).
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |