External wastegate.... HECK YES !! I think back pressure is a huge issue on this motor. A bigger turbine/turbine housing adds too much lag, the equalizer? External wastegate.
I don't care about external wastegate noise/sound. I don't care about boost control (which is improved greatly), I don't care about shiny parts, I care about lower EGT's, I care about less back pressure, I care about a more effective exhaust system. (If 30% of your exhaust flow is dumped via the external wastegate, you've effective increased your Dowpipe/catback size by 30%.
I've researched it a little on smaller exhaust housings and turbine wheel applications and when I can, I'm def going that route on a cyborg. I do think the effects/gains will be less on a larger turbo vs a smaller one, but none the less, if your gonna go all out, GO ALL OUT.