Does the exhaust size matter that much?

[819_FLY]

Turbo cars need as little restriction as possible, due to the flow of exhaust gasses backing up and interfering with the rotation of the turbine wheel. For many years people have said there is no point putting a 3" system onto a car with 2 litre displacement as it is pointless and the decibel rating would be illegal. Even going 2.5" on some cars isn't beneficial. 2.25" has been a solid performer for many cars running NA with improvement with both noise and performance. up to 5% would be a realistic figure when talking performance increase with a new system on a stock engine.