"In terms of vectoring into the porphyry, has there been any...

"In terms of vectoring into the porphyry, has there been any improvements in the resolution of Seismic technology since the original survey to assist with pin pointing the top of the Porphyry?" - yes.

Now 2D and 3D seismic surveys cost lot less and are lot more accurate. I've seen few presentations on how these survey work and how deep they can go while keeping the accuracy intact is insane. And when it comes to porphyry I think seismic surveys should be a must as they reveal the plumbing of the system.
I spoke with few Geos who are right now exploring for porphyries and did not get positive response - some sighting costs while ignoring the cost of the deep holes that keep producing not much in terms of grades or vectors to narrow down to the high grade zones. Some are clearly overdue for retirement.

Escondida is excellent example as it had very little magnetic signature but when they did seismic survey it showed plumbing system that looks like a Christmas tree. No wonder it is such a great deposit.

all my own thoughts..