Hi guys just doing some research and found an intersting article on the garret website about how to work out correct sizing ect for turbo chargers
Garret Turbos
Has some other more basic info there too with all there models with flow caractaristics ect.
Im looking at changing my GT2876R to a GT2871R more response with about 50 more hp flow

It sounds like a classic case of 'less is more' with your setup.
It's all a matter of balance, & an extra 50hp kind of helps to set the balance in your favour.

that page has tools to answer questions like what turbo should i use and is this too big.

they make 2 turbos that are well suited to ALL A series motors, and several others as more specific options.

look around the site there's lots of info from basic to advanced with formulas.