What makes the 20th Anniversary Turbo TA so special is that it is a complete mechanical package, and not just some tape stripes. Starting with the engine, Pontiac borrowed Buick’s 3.8 liter (231cid) V6 turbo powerplant from the fabled 1986-87 Grand National. Some difference exist between the TTA motor and the GN version. Different heads were necessary in order to squeeze the motor between the strut towers. These heads, adapted from the transverse FWD version of the 3.8 liter motor, have the added benefit of improved exhaust flow and combustion chamber design. Subsequently, different pistons were required in order to maintain combustion chamber volume. Other changes to the TTA motor are a cross-drilled crank, larger 12 fin/inch GNX-style intercooler in place of the GN’s 10 fin/inch design, specially-designed stainless-steel headers, higher-pressure Bosch 237 fuel pressure regulator, and a recalibrated engine control module.
Mark Grable, writing in the March 1989 Motor Trend, noted the Turbo Trans Am’s “250 horses…seem much stronger than run-of-the-mill horses.” The reason is simple. Although Pontiac officially rated the engine at 250 HP, in reality it developed an honest 301 HP on the GM dyno.