The LB9 is a 305-cubic-inch (5.0L) Gen-1 small-block Chevrolet V8 fitted with the Tuned Port Injection (TPI) system — long port runners feeding individual sequential fuel injectors. TPI swapped carburetion for what was, in the mid-1980s, GM's most refined road-going EFI system; it gave the engine strong low-and-mid-range torque at the cost of upper-rpm breathing.
By 1991 the LB9 made 205 horsepower net at 4,400 rpm and 285 lb-ft at 3,200 rpm. (Period 'net' ratings are not directly comparable to the 'gross' ratings of 1970-era engines; net ratings are taken with full accessories and production exhaust, and they read 15–25% lower than the same engine measured gross.) The engine paired with both manual and automatic transmissions; on Trans Am and GTA cars it usually ran behind the 4L60 automatic.
The 5.7L L98 — same architecture, larger displacement — was the upgrade engine in the same chassis. The 5.0L was the price-of-entry F-body V8 in those years; the 5.7L was the package's serious option.
