A bigger turbo is meant to generate higher boost pressures which will in turn increase power. Getting a bigger turbo serves no purpose if you are going to stay boosting at 10 psi.If anything, a bigger turbo boosting at the same pressure would give you more turbo lag. If you want to stay at 10 psi then it would be best to get a smaller turbo to get faster spool up.But really if you want to increase your power... Turn that boost up!