I sold a 1991 Allante in June of '18. It was an honest, documented 19k mile car. Very beautiful condition. I loved the car itself but anything I had done on this car was very expensive. During my 6-year tenure with the car, I replaced the ABS pump, fuel injectors, A/C compressor and related parts, oil pan gasket, belt tensioner, muffler. power window switches and radio speakers among others.
I was advised by the Allante expert I used in West Palm Beach to be sure to keep the brake fluid flushed regularly to prevent brake problems. He also said the coolant must be changed often too to help prevent problems with the head gaskets.
My point is that these are high-maintenance cars, very specialized, often difficult to diagnose problems on and very expensive to repair so if you aren’t willing to accept this before buying one, then don’t!