I think there is only a handful of cars that have done this and they are all from ZZP as far as I recall.

I saw on 3800pro.com that Intense had been working with STSturbo.
Did you guys ever get a chance to try anything with the L67?

Please try to stay on topic. This is about twin-charging. ADDING a turbo to a SC car.

I actually read up on the twincharging with an M90 and a turbo, and from what i read it'* more of a PITA than anything and you'd be better off just running a turbo.

It'll take ALOT of custom hardware and a custom boost controller. There are perhaps 4 or 5 people on this Forum capable of fabricating and building this. Anyone else would pay a premium for the custom work.

Yes, at one time I considered this, and it almost happened 4 years ago (free labor and parts at cost, but it would have required a 900 mile drive and a week for the work).

If I've read previous discussions correctly, the tricky part is sizing the turbo.
The supercharger will multiply boost from the turbo and the turbo needs to be relatively large so it doesn't become a flow restriction.
IIRC this is comming from discussions with ponticajeff over at 3800pro.

Building the Twin Adder setup isn't overly difficult, or buying an off the shelf setup and keeping the */C isn't hard either (at least for the S2/3).

The hard part comes in when you need regulate boost. There are a few different ways to do this and the easiest involves using the stock BBV setup. But you will extremely restricted on boost levels, you'll never be above 20lbs(I don't remember the exact number, but IIRC its ~14lbs).

ZZP/Stamma can build the boost controller for you, but IIRC it was very pricey.

Bottom line, for ease and reliabilty run a single turbo. 7lbs (non I/C) on an L36 bottom makes for an extremely reliable quick car.

Search for pontiacjeff, he'* doing pretty much exactly what you're asking about on a 96 SSEi.