What about converting to a hydroboost brake booster system and getting a lot of mounting cubic inches out of the dside underhood? I still like the one big turbo idea, unless the exh path on the crossover is too long.

Since all the load the intercooler will see will be short bursts (I wonder how long it takes a TT Monstero to get to, oh, 140ish...), why not go water air and save that space, too. Or since you have all that room for tanks, methanol/water injection.

The 3.5 intake is a two path for helmholz tuning at both low and high rpms, with a vac actuated changeover flapper. If you boost it, I'd just remove the 6 little throttle plates and the shaft, and seal the shaft holes on each end. I think you would still get ram tuning at the two ranges, just lower in amplitude, on top of the boost. free power.

Mitsu only used dohc heads because they already had them ready for the 3.0tt 24v, and the sohc24v heads were not ready yet. As soon as they had the sohc's ready, they used them on everything. I can't remember if the 3000 kept the dohc's on the 3.0 variant or not. You'd know better than me...

Unless the cam timing/lift is different, the only advantage I see to a dohc over an sohc with the same size/count of valves, is the lower mass in the valve train minus the rockers. Friction in the dohc may be higher (do they have roller followers? do the sohc's have roller rockers?).

Does the 3tt motor electronically control the boost?