Found oil in the Airbox

[KAT600]

A few days ago while riding, I noticed that from 6000 to 10000 rpms the engine would miss or lag. I pulled the air filter and box and noticed that the drain hose was missing. I replaced the drain hose with a similar hose. The air filter needs to be changed as it has oil on it. I checked all the vacumn lines and they seem ok. The clamps on both of the middle carb intakes were loose, so I tightened them. After that she ran better than ever. The bikes a 1989 600. I'm the third owner. Yesterday I rode home after a very heavy rain, during which the bike was parked outside. She ran really badly. I stopped and ran the engine and revved it up a bit, as I thought it might just be wet. After getting home I noticed gas gathering at the bottom of the #1 carb. It wasn't dripping, just pooling at the bottom of one of the screws. So tonight I decided to pull the carbs and clean them. When I pulled the air box and filter I noticed a small amount of engine oil inside the airbox. I just cleaned the inside the other day when I worked on it. I still have to pick up a new air filter tomorrow, hopefully I don't need anything when I get into cleaning the carbs. I'll be working on the carbs tomorrow. Any ideas on whats going on, or possible things to be looking for? Should I be thinking about replacing vacumn hoses? Any imput would be helpful. Thanks.