Any oil in intake side? If you are running an intercooler pull the lowest hose from the intercooler and see if there's oil in there. If there is , you may have oil pressure thats too high going to the turbo, or the seal may be blown.
Are those turbos coolant cooled as well? If they are, I wonder if your turbo's center housing (chra) has cracked and allowing coolant past the jacket into the turbo. Hard to tell without taking it apart. Rare for that to happen, but I have seen casting flaws cause this in the past.
Those spark plug electrodes look burnt. What brand and model plugs are you running? And most very important, where did you buy them? If you bought them on Amazon or Ebay there's a very good chance they're fakes branded and packaged as what you thought you were buying. I'd suggest a set of NGK BKR7E-6097 copper plugs for your next set. You want to change those at every oil change if you do run them, they're forgiving against detonation and a solid choice for a no brainer plug. For spark plugs make sure to buy them from your local auto parts stores, or their website. Never order spark plugs on Amazon or Ebay.
If I were you, I would 1) check the intercooler for oil, drain if there is any in there and put the turbo back together. 2) get a set of NGK BKR7E 6097 plugs from your local auto parts store to run next. 3) check your base timing with a timing light and adjust distributor if it is off. 4) Are you running OEM ignition coil? If you are check it closely for swelling or cracking and replace if necessary.
If you want to scope the cylinders a good cheap scope I have and use often is this one:
https://amzn.to/3uyntg0
Let us know how it goes.