How to get more kw

Hey there, i like to tune cars. But just tge optical part. Finetuning isnt mine and the problem is, if i take a tuning setting from a pro, then i cant change spoiler and wheels. But if i tune the car by myself and buy eveything i can buy for it the expert is about 400 kw more then mine… How? Sry im german.

Without more specific information, and assuming “kw” is where I’d say “hp”, I’d guess that the “expert” has performed an engine swap or added a turbo where you have just upgraded the stock engine.