I would 100% avoid milltek unless you're fitting HFCs. I had a milltek for about a month and was instantly disappointed as soon as it was fitted. Its quieter than OEM. swapped to an ark grip after and never looked back. Sold it to a forum member who has HFCs and I hear it sounds really well.
Fitted with decats and it totally changed the sound lol. Imo it's verging too loud under load but nice n quiet ticking over n tootling about.