The block-off-plates should only be used in conjunction with a SAIS/AIP bypass module. Two plates are required for your engine. Note that the 4.7L plates differ from the 5.7L plates – you must have the correct plates for your application!
The SAIS/AIP Secondary Air Induction System includes air tubes that connect to the rear of the exhaust manifolds on each side of the engine. The block-off plates fit in between this connection to stop exhaust gasses from backing up into the SAS/AIP system when used with a bypass module. The block-off plates prevent exhaust gasses from leaking back into the SAIS/AIP valves.
For codes P1441, P1444, P2440, P2442, you ‘must’ install the exhaust block-off plates. We highly recommend installation of the block-off-plates in all circumstances, but for these 4 codes, the bypass module and the block-off-plates are required to prevent these codes.