dont listen to him, he's just a bitter old mk4 owner and has realised he made a mistake gettin rid.
The 1.8T is a good platform and good power can be made from good money
The best start is to buy a mk4 1.8T fitted with a K03s turbo, so this normally means buying a AUM engine code model.
From a good Milltek system, larger downpipe and sports cat, panel filter, 007p re-circ valve, Forge TIP and remap you can expect power around the 220bhp mark on a good engine. This will set you back around £1000 which for an 70-80bhp gain is fairly good.