Why would you go down in turbo size?
A T28 series is too small for this size engine. I have my own tuning business and i would definately choose a T3 series turbo again, but with a bigger compressor trim. Im putting a T3/T4 on my own, this will give a good boost scale with about 1 bar(14,5 PSI) from around 2300-2600 rpm. I never put a T28 series turbo on an engine over 1800ccm