I purchased this downpipe with hi flow cat, and available gaskets during a Black Friday sale and couldn't be happier. The quality is second to none. Fitment is spot on, and bolts in like a factory piece. The grade 10.9 hardware included is an added bonus. This is the only downpipe on the market for the Regal GS that has an inlet flange diameter that actually matches the turbo's 3.5" outlet. I noticed increased mid range power, smoother power delivery, and a slightly more aggressive exhaust note.