Hi, past owner of RS220, and did pretty much the same extent of mods that you're proposing - all installed by Renotech who were awesome. In terms of downpipes and tbh the rest of the parts you're proposing, give GT Performance in France a look - they were pretty cheap and easy to deal with. Find them through Facebook. And also replace the inlet pipe at the same time (through the Airtec ebay Store). On arriving for the tune, I had the tuner tell me there was no guarantee that the stock airpipe would be in one piece by the end - I changed it shortly thereafter. Also be aware that the inlet pipe for pre 2018 is different to the one for post 2018 cars. Best of luck.