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

what BHP are you aiming for??

It should help a little but it is defiantly not a cure. It depends where on the comp map you are. If you need lots of shaft speed you still need to get the ex gas through the turbine to turn the shaft, regardless of how restrictive it is. A large wastegate will not help here.