1989 560SEL

I've seperated the air duct housing (rubber boot) from the air mass meter in order to replace it. Upon dissasembly I've found that everything is coated with a wet varnish like gunk. I assume this is old gasoline. Is this normal or is the fuel distributor leaking? The car has 142,000 miles and is running fine. With that many miles I didn't expect it to be clean inside but I want to check with the forum if it is normal to find this.

I'm going to clean the air mass meter with carb cleaner before installing a new air duct housing and flange.

Thanks
~Dave