How to verify that knock sensor and evap pure valve were actually replaced? They do not appear to have been on my 82 year old mother's 1997 Maxima GLE..

If they look old,they probably have not been changed,she was just took by a shyster mechanic,the only way to confront this would be go to the mechanic,and tell him you are having problems, with them,as you and i know they have a lifetime warranty on them,tell him you need the invoice so you can replace them,,,,this will get him,when he can,t produce it,with the proper date,then if he doe,s not want to cooperate with you,report him to the BBB.