ok so my car would splutter and is hesitant under 2000rpm when crusing. When i go over this its perfect. It started suddently like 5 months ago. I heard it might be overfuelling. I got a BLITZ ecu, decat, front mount, stanrd air filter, turbo and boost. What is causing this. i can smell petrol and the plugs have dark carbon on dem. The car aint as economic as before. It goes well but just plutters under 2000rpm like its having trouble moving but after 2000rpm its perfect. How can i fix this? anyone got solutions????? but I had all these mods before and it was fine so something has gone wrong?