Pull off your hot pipe going to the intercooler. Any oil? How many miles on the car? As stated, do a compression test. A leakdown test would be in order too. From your description of the problem, doesn't sound like a headgasket issue. If it was, your overflow tank would be spewing oily milkshake everywhere (or your oil would be overfull with coolant). Might be time to take it to a pro if you are not equipped to diagnose the problem. In the meantime- keep a close eye on the oil. Last thing you need to do is starve it and blow it up.