We have K&N Cold air intakes.
Iv taken the bluefin route and rex has Revo. Both of us are happy with the results and it makes a very capable car even more capable
Not sure what exhaust rex has but I have a R20 backbox and going to put a non res midsection eventually. Im not hardcore enough to use a different downpipe or decat it but people have done this on more heavily tuned tsi 122/125 with good results.
Im also retrofitting an air intercooler as the engine only has watercooling so itll become twincooled. Help keep temps down from the remap and a little bit of performance too potentially.
Theres lots that can be done but fact is not many people have bothered to do up these engines so writeups etc are rare compared to the GTIs and R's