I have a pipercross panel filter in mine, it literally made zero difference to the performance and sound. I got it for a little extra intake sound, but it's no different. I'd be expecting the same from the Racingline filter. Save your money for an aftermarket intake. The HFI carbon intake is nice but it's eye waterngly expensive.
I'm also interested in the OEM+ tunes, but there's just not enough transparency there. No prices listed anywhere or dyno graphs on their website, just a bunch of "trust us, it's great" talk. Going to need more than that to convince me to spend $1500+ on a flash tune. It's a new product though, so hopefully in time there will be more info available.
As for springs VW Racing sport springs, H&R 25/40 and Eibach Pro Kit 1 are popular choices.
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