Just wondering what could be the culprit. My guess is the seal that goes behind it, but is the any other places that it could be coming from?

Thanks in advance.

 

Opti seal in the timing cover is the most likely cause. Could also be the water pump drive seal leaking down onto the opti as well (assuming you have a stock mechanical pump).

Since you have a vented optispark, there is less than a 1% chance that you're getting oil from the vacuum line if the backflow prevention valve is busted or removed.

 

dang i type to slow. lol. once i posted i see ramair is on it.

yah or through the opti shaft seal. did it have oil on the outside of it? only other way is through the vent and if thats the case u should have oil in the air intake.

 

What is the backflow prevention valve and where is it located?

 

The small blue thing is the backflow prevention valve - the large one is a flow reducer. These are the vacuum lines attached to the optispark.

Like I said, a small chance. It's unlikely.