It is unusual to see a car needing such drastic work as usually, a flush, refill with LHM and perhaps recharge of the spheres is all that is needed. Meraks still suffer this problem. The small 2 litre home market model is really too underpowered for the car and is best avoided. Parts availability is good and running costs are generally low in this company. The Biturbo range was a new departure for Maserati.
Differentials can cause problems - the unit is set very low to the ground and is easily knocked.
The differentials lose oil and unless regularly checked this quickly causes overheating and failure. Other than the special units used in the Ghibli Cup cars replacement turbos are widely available and not expensive. Common service items will be found in your local parts store. These cars are woefully undervalued in the market and any model can be picked up very cheaply. Unfortunately, their low value discourages owners from performing proper maintenance and much of the Biturbo's poor reputation for reliability stems from this factor rather than any inherent design flaw.