Getting oil in my coolant. How is this possible?

Did you overfill your engine oil?

Had a similar experience in my car years back.  I found oil in the radiator and the engine overheated like crazy.  Apparently the head gasket was warped, causing the engine oil to leak into the coolant.  If it had gone any worse, coolant could have leak into the engine. 

Sorry, I am not much help with your situation but I am guessing some gasket had failed.  I am sure there will be an engine expert chiming in. 

yes, usually a cylinder head gasket that has gone will cause the oil in the coolant and vice versa.
BGB

How do I know if it is a head gasket? and now what are the appropriate steps to clean the system out? its an 02 S4 should i be using sealant on the gasket if it is the gasket?

I guess it depends...  if it's just the matter as the seal, you can simply replace it.  However, in some cases, the leak is caused by the actual warping of the head, which requires machining.  I would have a tech check it out and pinpoint the exact cause (and the severity) before you move forward with it.  my 2 cents.

You just swapped in hi-comps, so you had the heads off.
Likely a bit of oil got into the water galleries then.

You used new head gaskets when you put it back together, yes?

BTW, starting a new thread at each obstacle eliminates the backstory that can help folks figure out what's going on.
Getting oil in your coolant 'out of the blue' is *way* different from getting it after you've done top end work.

ahhhhhh the rest of the story!