Quiet possibly could be oil residue that was inside the MAF and or pipe. K&N oil would have a slight reddish tint to it. Might take your MAF pipe and MAF sensor off and check for oil residue. One other possibility if you were running a stock location IC, could be that when you let off and the turbo spins backwards, if there was any oil pooled in the bottom of the IC, it could suck some of that oil back through the turbo. That's a huge pressure spike going from WOT 28psi to shut off.
The dual bb 6776R turbos, do not have dynamic oil seals like the journal bearing cousins, they have a encased bearing system cartridge. This is also why they do not require a lot of oil for lubrication. The silver restrictor fitting that comes with the turbo from PTE, is setup for a -4 An feed line. In some cases (excessive oil volume and or high oil pressure applications) I had customers who would step down to a -3 An oil feed line and in doing so, would cure any oil leaking issues on the compressor and or turbine side. Last I checked, PTE still offered a -3 An restrictor fitting for the dbb Garrett based turbos. That would be the last ditch effort if everything else was covered. Also, dbb cartridge equipped Garrett turbos do not like to see oil pressures over 85psi. That is the easiest way to make them leak. Aka, excessive oil pressure.
Just a thought or two.
Patrick
