I think it is pretty well known about the issues the GT2876R and the issues with the turbine side not being able to flow enough to get rid of the flow the compressor can produce.
In fact garrett even quote that this is a problem. and say it is best suited for unique applications such as asymmetric turbo installations (only 1 bank driving a V6 turbo, and it is not recommended for general performance applications
Anyway - running a 40mm external gate, will this fix the issue? as it gets the flow away from the turbine, or is turbine "choke" going to be an issue with this turbo no matter what you do?
Anyway to get around this or best to avoid? anyone had any success with it? just thinking about better spool than a GT3076R
link to garrett