The 1992 to 1994 Engines the differences are: Intake manifolds, fuel
injection type, cam grind, valve covers, throttle body type.

    TBI is Throttle Body Injection. This means the Fuel Injectors reside in
the Throttle Body (like a carburetor with fuel injectors inside instead
of venturis or "barrels"). This type fuel injection uses a intake
manifold similar to a Carbureted  engine. On 1990's TBI 454's they are
Carburetor intake manifolds with a adapter plate for the TBI unit.

    CPI is Central Port Injected. The Throttle Body  handles no fuel, just
air. The Injector(s) sit in the middle of the lower intake manifold with
plastic fuel lines that run to the head port. The lines carry the
atomized fuel, and it mixes with the air at the head port when the
intake vales open. similar to GM Multi-Port Fuel Injection, except the
Injector(s) are remote mounted, with feed tubes running to each cylinder
instead of a injector at each cylinder. CPI injection units are known as
"Fuel Spider".

    CPI engines use composite plastic valve covers, TBI engines use stamped
steel. The cams are supposed to be different grinds. Yet are close
enough if you convert a TBI to CPI, or CPI to TBI, they run just fine.

    Later 1995 up CPI engines have a Balance shaft, that is above the cam
galley, running threw the lifter valley.

Charles