Early in 1990, the 1991 Camaros debuted. Big changes occurred, as all Camaros received a facelift in the form of a ground effects package for both the RS and Z28 models, while the IROC-Z was no longer offered. The Z28 also featured a high rise spoiler and non-functional hood "blisters". The 1991 Z28 also received a new wheel design to accent the new body that the B4C "Special Service" option was made available to law enforcement, the government, and military agencies. The B4C amounted to little more than a Z28 powertrain and suspension in the RS. (Car Craft Magazine refers to the B4C as a 1LE equipped with air conditioning; although this is slightly erroneous because in 1991, the large brakes with PBR calipers from the 1LE package were not included with B4C.) Just under 600 B4C Camaros were sold for 1991. Power ratings on the 350 TPI were as follows; 245 hp (183 kW) at 4400 rpm and 340 lb·ft (461 N·m) at 3200 rpm. Power rating on the 305 TPI motor were as follows; 230 hp (172 kW) at 4200 rpm and 300 lb·ft (407 N·m) @3200 rpm. Rumors say that these numbers were slightly underrated by GM, but this has not been investigated.
Beginning with the 1991 model year, GM pioneered some modified assembly techniques with the F-body Camaro and Firebird which would be carried forward into the fourth generation. Different seam sealers, structural adhesives and body assembly techniques were employed in key areas, in an effort to reduce squeaks and rattles and improve the perception of quality.
Source: Wikipedia (original)