It sure wasn't the engine.
Believe it or not, there was a Ferrari 348 Speciale, although it was built in very, very limited numbers. 100 examples, to be precise, and only for the US market. In fact, just 35 coupes were made. From 1992 until 1993, the 348 Speciale existed and, compared to the standard 348, the coupe specifically, it featured a new front spoiler, front grille, body color bumpers and rocker panels, and better tires. The 3.4-liter V8 was also upgraded, but only because it was done so for the just launched 348 Spider, so the Speciale benefitted from that.
To sum the 348 Speciale up, it had somewhat racier styling and a 12 hp bump (300 to 312). Clearly Ferrari could have done better, but that's what the F355 was soon for. Oh, and there was one other noteworthy 348 Speciale upgrade: it offered the same carbon fiber racing seats found in the iconic F40.
That alone is wicked cool. Back in 1993, when Motor Week reviewed it, the 348 Speciale cost $112,000 (heck, the Spider was at least $122,000). In today's dollars, that's about $190k. For the record, the 348 Speciale's eventual namesake, the absolutely brilliant 458 Speciale, cost nearly $300k.