As Steve mentioned not much readily available tuning parts or kits are offered for the model except for the engine (which is common with Integrale) probably because of the rarity and unpopularity of the model. So have to be looked for custom order parts, fabrications and figuring out some things at different stages as don't have much projects and will be faced unknowns, which will make the project more difficult.
Also generally for some serious projects are necessary people, which are first big fans of the model and second to be ready to spent a lot of money on the car, so to be wealthy enough at some sort to have enough spare money and Integrale's owners are more wealthy than Q4 ones . 300hp can be achieved without so much money, but for more serious projects a lot of $ is needed ...