Q: The gasket is deteriorated in the intake manifold gasket

If the gasket does have to be replaced it is replaced as a "whole". There is no partial intake manifold gasket. Please note that the code you are writing in about, Diagnostic Trouble Code P0171, can set for many reasons other than a failed intake manifold gasket. Not only does the gasket and adjacent assembly have to be tested for leakage and correctly diagnosed as "the" fault behind the code setting but all the other possible causes of the code setting have to be considered as well. If you did not receive a conclusive diagnostic, preferably written, indicating that that gasket must be replaced, then prior to the work it really has to be diagnosed. The other common causes of Code P0171 include the MAF (Mass Air Flow) sensor is dirty, faulty, or in some cases the MAF sensor has leaked the silicone potting material used to protect the circuitry. In addition to intake gasket leaks, there could be a cracked vacuum or PCV line/connection, faulty or stuck open PCV valve, failed or faulty oxygen sensor, sticking, plugged or failed fuel injector, low fuel pressure due to a possibly plugged and/or dirty fuel filter and an exhaust leak anywhere ahead of the first oxygen sensor. If you desire that the intake gasket be diagnosed and replaced, as needed, simply request intake manifold gasket repair and the responding certified mechanic will make the replacement as well as advise you as to these other possible causes of the code setting.