I had similar problems due to previous owner,
I replaced the oil trap box, the hoses and flame trap, if you do this be sure to order the intake manifold gasket and the throttle body gasket, clean the throttle body out at the same time, pull the intake manifold back far enough to access the oil box (makes it a whole lot simpler). Order a new oil filler cap seal too from FCP whilst yer at it. I believe a lot of oil eventually migrates to the top of the tranny and drips. That oil ruined my tranny mount, but it was only a $20 rubber bushing and simple to replace.

The benefit to doing all this is now you are back to a known quantity. Its kinda important to prevent the engines rear main oil seal from blowing to stay on top of the oil trap venting.

While you have the flame trap off for cleaning, remove the oil filler cap and make sure you can blow air (unrestricted) down the large diameter hose that connects to the breather box on the side of the engine block. The air will escape the crankcase through the open oil filler. In some severe cases, the breather box becomes clogged up, in which case cleaning the flame trap alone won't really fix the problem.

Some poeple clean them once a year, others twice a year.
But twice a decade? YES it will help. That soft rubber seal under your oil cap is no match for high crankcase pressure. It'll coat the whole engine in no time. And any other leaks you might have will be greatly reduced if thats not the culprit. (though I'll bet it is.) And when you've cleaned or replaced everything you should, don't forget to ream that little vaccum hose neck through with a drill bit of the proper size. Same deal on the intake manifold side. (or better yet replace the whole thing.) At high crankcase pressures, you can blow some pretty big and expensive seals. Hurry and do it. The 700/900 FAQ has the pics and info.