Oil Leak

Hi guys,
I have a 91 Celica GTR 4WS.
I have a oil leak around the engine somewhere, it has leaked on to the right side drive shaft and has being flung everywhere. It does not loose oil very quickly, about 100ml per 500km. Its not the PS fluid either, the level has not changed. The rocker cover gasket has been replaced about 20'000km ago. So im hoping its not that, but i cant identify where the oil is comming from.
Has anyone had this problem before, i have to take it in for a wof in the next few days, so im trying to get it sorted by then.

Any help/advice appreciated.

Luke

Drive shaft oil seals???????

I dont think it has come from the drive shaft seal, as the transmission fluid would be leaking, but it stays at the same level. The Engine oil level is going down, so im pretty sure the oil leak is engine oil. At frist i thought it was burning oil, but there was no signs on the spark plugs. I think it is leaking somewhere near the top of the engine, and running down onto the drive shaft.

Any ideas ?

in order of probability
1. torn engine vent pipe (between rocker cover and inlet pipeing
2. Rocker cover
3. Oil filter
4. Cylinder head gasket
5. Sump casket (hardly ever goes) it near the bottom anyway.
6. Knock sensor or some other sensor loose.
7. Cam shaft oil seal (either end)

thats all I can think of for now.