From what I gather, the conventional wisdom is that Series II front exhaust manifold is more restrictive to flow than the rear.
But the only actual numbers I can find are from this old thread...
http://www.bonnevilleclub.com/forum/...ght=A&start=20

...and they completely contradict that idea; however, there are some questions about methodology and the possibility that the numbers were "in the wrong columns."

So, has there been more recent flowbenching (or other verification) done on the front versus rear flow on Series II exhaust manifolds?

This isn't complety off topic but, another alternative for a front mani could be to have a tubular fbody 3800 manifold modified to fit. They came with tubular then switched to cast IIRC.

I guess this gets to the heart of my question...is there a proven need (performance-wise) for an alternative front manifold?

Consensus says "yes."
Data in the thread I linked above says "perhaps not."
Is there any newer data?

I didn't have data logging at the time... all my testing said yes, there is a noticable flow improvement from manifold to PEM and another difference from PEM to header.

I have not heard about any newer data or testing done since that thread last year.

However, I can most certainly speak to the felt improvement using front and back PEMs over stock manifolds. Mine were installed last October with very nice results! Again, I have no data, since I did not do before and after testing, but I can tell you that my scanner doesn't show any issues with lean banks either front or back. And my car runs much stronger through the power band with smoother shifts and throttle response.

A worthy mod for those not wanting or needing to go all the way to headers, IMO.

Or those (like me) living in an urban California county, where headers (or any other exhuast mod) are illegal for street use on most cars.

Slightly off topic...

I could never quite understand the reasoning behind that law in California. I know that in both eprevious vehicles that I've installed headers, I gained both power AND increased gas mileage.

I know, I know, it'* really about total emissions...

But when I think about the better fuel efficiency that can be had using headers, I equate that with lower total emissions for the equivelant amount of power.

That having been said, PEMs would fit your requirement just right. They will look stock but provide a power and efficiency boost.

I thought TOGs were legal in Cali?

but...are they approved for his car?

I don't even know for sure if they are still approved in GPs since they aren't made by the same people anymore. Thats what the ? was for.