Okay So I have a 2002 4runner and Im smelling some exhaust and some burning oil. I had the valve cover gasket replaced in 2017 and I replaced both catalytic converters as well as the muffler also in 2017. I pulled two spark plugs and noticed oil on them so Im thinking the plug tube seals ( as far as I know should had been replaced when the gasket were) Although after 5 years shouldn't need to be replaced. but I was calling around and wanted to have the valve clearances checked and shims replaced if need but several people said you dont adjust them. Called the dealer and they said they would do it with a new gasket for the covers for $789 which was way cheaper then the people who said they would do for $3100-3600 ( i think they were just doing a complete valve job) I also saw the timmy the tool man video on this. so what is the consensus on this. again Im only considering this because it has never been don in the 257000 mile it has on it and the burning oil( not a lot) and exhaust smell