Plastic Or Rubber In The Airbox

[HoseIRMC]

Digging around cleaning the bike up checking vacuum lines to see why my 2001 would surge at constant throttle and found chunks in my airbox. My motor was rebuilt less than 2k miles ago and had the pair valve mod removed. I'll provide a few pics. What is this stuff and where is it coming from?

 

[HoseIRMC]

Here's another pic... It is coming out of the PCV tube...

 

[RedBull]

Perhaps it's foam particles ~ falling off from the air box seal . . .

 

[HoseIRMC]

I thought that at first but this stuff is covered in oil and its mainly towards the back of the airbox where the PCV tube comes up. I'm going to block off the tube with a filter and see if it gets better or worse. I'm worried it could be a valve cover gasket. Do you of any way to replace that foam with something that holds up a little bit more?