For downpipe, you just need one that suits a Mk5 GTI. The Pirelli has a larger k04 turbo, but the downpipes are interchangeable. The absolute cheapest I would recommend would be xforce. All the super cheap ones (sub <$500) are absolute garbage and will crack at the welds and most dont have a catalytic converter either so they are illegal.

Volkswagen Golf GTI MK5 and MK6 Downpipe with High Flow Cat – Rob Bliss Exhaust

CTS TURBO MK5/6 GTI, A3 2.0T FWD DOWNPIPE w/Catalytic Converter – Dub Addiction

Integrated Engineering 3" Catted Downpipe | Audi A3 8P & Golf GTI MK5

For HPFP, depending on your budget you can just upgrade the internal parts of your existing HPFP (cheaper option) or you can buy a whole new HPFP unit with the upgraded internals already fitted. I had the Autotech on my car and it was good. Ive got a DIY guide if you need it.

Autotech High Volume Fuel Pump Upgrade Kit 2.0T FSI - 10-127-100K

034 - High Pressure Fuel Pump Upgrade kit - 2.0T FSI EA113 - Audi/Volkswagen– VAGPARTS Australia