In 1984 and 1985, the 2.5 L V6 models utilised a single Weber DCNVH carburetor under a smooth aluminum alloy plenum fed by twin IHI turbo chargers (one per bank of cylinders). Maserati, U.S. dealers, and sports car enthusiasts began experimenting with intercoolers for which many variants were fitted and mutually endorsed by Maserati. Intercoolers included air-to-air (two variants: top mounted assembly which was not as efficient as the separate side-mounted versions) and water-to-air intercoolers, all produced by Spearco. In 1986, the 2.5 L V6 models switched to a Weber 34DAT carburetor which was proven to be less efficient and more problematic to maintain than the Weber DCNVH used previously. On initial viewing of the 1986 Biturbo engine bay, the aluminum alloy plenum is finned with a slightly different footprint and the intake manifold was specific for that model. Similar experimentation with intercoolers and placement continued through 1986 models. However, the side-mounted water-to-air intercooler became the standard variant utilised until late 1986 or early 1987 when the intercoolers were placed by the Maserati factory, outside the engine bay located in front of the radiator where they remained throughout the remaining models in the Biturbo family tree.