1988 Peterbilt 378 3306 diesel turbo issue

My first post here. I hope I'm in correct place.
1988 Peterbilt 378 3306b diesel engine. I was having oil in exhaust smoking out issue.. After, adding vent for crankcase fixing intake restrictions I still had oil dripping from between exhaust and turbo connection. Thinking it was seal in turbo. I had removed turbo and wet oil residue in turbo exhaust out and all through exhaust. The exhaust manifold was fairly dry at the mount point for turbo. I installed new turbo , changed oil and filter, lubricated oil inlet at turbo and cranked engine without starting to get oil into turbo prior to start. Started engine and ran to clear smoking oil residue from exhaust. As it was running I kept inspecting and noticed after a few minutes oil dripping from turbo and exhaust pipe connection. I shut it down and disconnected exhaust pipe from turbo. Fresh clean oil was pooled up at this point. You can imagine my optimistic day dashed on the rocks. I took a break to process this. Any suggestions for oil source? I'm going to check to insure the oil drain is not slow. Upon reassembly I thought cleaned both inlet and outlet tubes. Maybe block restrictions? I out in just the correct oil amount . Full line on dipstick. 10 gallons of oil . Thank you in advance for any help with this.

 

Air filter is new. Forgot to mention that..

 

Yes I meant thoroughly...when you say trouble can you be more specific.
With the old turbo off, the exhaust manifold ports to turbo were not oil soaked. There was oil coating the turbo exhaust side on back .I'll try to attach photo

 

When I started this project I discovered that the air filter was installed backwards. The tapered shape effectively plugged air flow . Big restriction. I don't know how long it was driven like that. It's installed properly now. The problem persists . The truck runs very smooth. I would expect a little rough run with dead hole. What kind of damage would be caused with operating the truck with the filter backwards?