Well, following the disappointing news from Larini (they're currently developing some products for the Maserati 4200 so don't have time or see the value in refining the Ghibli cat replacement products) I've ended up ordering an OEM Maserati exhaust.
Maserati made a de-cat version of the front exhaust exclusively for cars being shipped for the Saudi market and there's still some units remaining in stock at the factory. Seems there's not a high demand for these parts, since the price is very reasonable... I'm saving almost 50% over the Larini system. It won't look as nice as the Larini system, but it's still made of stainless steel and since it sits beneath the car you don't see it anyway. So hopefully it will arrive while I'm away on a business trip and be ready for me to have installed when I return in a week or so.
I've also had a quote for the wheel spacers from a German supplier. However, I've changed my mind on the front spacers, where I'm only going to install 3 mm spacers, since the wheels are already pretty flush with the arches. But at the rear, I'm going to install 10 mm spacers since there's plenty of spacer there. It should help the grip at the rear a little too.