1999 Volkswagen Passat Oil problem

I have a 99' 1.8t Passat. When I had 127, 000 miles on it the timing belt went. I had the head replaced and have always used synthetic oil in the car, even before the head was replaced. It was very clean! I recently let the car sit for about a month and when I went to drive it again the oil light came on and I could hear a loud ticking. (Not enough oil getting to the valves I excpect) What would be the cause of this and could I do something to fix it myself? I had the oil pump replaced a year ago, so I wouldn't think that would be the cause. Could it be that there is a blockage somewhere or sludge? I have noticed to that I have a loss of power as well, almost as if the turbo wasn't kicking in.