The S3 system in comparison to the one they offer for the LCR is huge. Over on SCN, 90% all have Milltek and while it's better than OE, I think there's improvement to be made still. There's one guy who back to back tested Milltek vs free(er) flowing custom and the custom system made better torque and a few more BHP, this was on K03s though. I think there's just me & two other guys who decided to be brave & try something different, turns out to be a good decision & she's now GT30 proof (with new DP anyway). The build quality of Milltek is good, very good but that doesn't mean that a skilled custom fabricator cannot match or better it if the materials are of equal quality.