2005 Malibu 3500 Eating Oil

I've got a 2005 malibu (not classic) with the 3500 V6. For some time now the check engine light has been on with the low catalyst efficeincy code. Recently it has started eating oil pretty bad too. Its got 135,000 miles. I remember something about the intake gaskets leaking allowing oil into the intake and thus eating oil. I can't seem to find anything about it though. You guys got any input on what my problem may be?

Not real sure, when I was a GM tech we had very little trouble the new gen v6s without the coolant through the intakes. On the old ones though, it was possible to get oil into the cylinders through it though. If you pull the spark plugs and narrow down to one cylinder that would give you a place to look. On the other note though, if it has been burning oil though that would make since for the effeciency code. The oil into the exhaust makes the exhaust to rich for the converters to handle. The bad part is that if it has run very long at all like that the converter is junk now anyway too. The oil in the exhaust will coat the catalyst and make it not work.