2010 mack pinnacle, replaced the turbo still have black stuff spewing out tailpipe

Hi, couple questions. This is a Eaton auto shift 10 speed.
was pulling a hill in pa and when it went to down shift the gear it was gonna go into just blinked and lost momentum to where it had to drop another gear. I replaced the fuel filters when delivered the load.
that was first incident, week later after going thru a toll booth it did same thing.
In between those times it thur a code an wouldn't regen, took to shop, they said turbo needed replaced, then they raped me while putting it in.

had the truck bout a yr now an the turbo has been my biggest bill thus far

Notices months b4 any issues that there was black stuff running down my tail pipe, mack shop didn't have explanation just said dpf filter may need cleaned but couldn't no til they took it off, but they just cleaned it b4 I bought it, so it only had like 50,000 miles on it by then. And I was outta town when bought the truck an had to wait for filter to come back from cleaning b4 I could leave with it so know for sure it been clean.

Now after turbo, I got it washed the other day an looked in mirror at trailer an seen black spec all on side, when stopped I looked at tailpipe an lot black liquid came out to go all over side trailer an run down pipe.
Kept eyes on tailpipe every other stop or so an sure black stuff come out pretty often.
any ideas why it does that?
and will it hurt my new expensive turbo?
then also the third time my truck wouldn't shift right I turned radio off an heard the engine sputtering like it was thinkn bout stalling out, is this the fuel pump? Or what should be my next step in this search after already changing fuel filters and adding treatment in fuel?