When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
On my L98 it's in the left valve cover; a breather vent line is in the right valve cover.
Pull the PCV valve (if you have one) and hit it with laquer thinner or brake cleaner, shake it and see if it rattles. Then clean & dry it and see if you can blow air only in one direction; if so it's fine. They eventually get gummed up and just need a cleaning.