91 350 SD smoke and miss at start
A recently purchased 91 350SD inline 6, 3.4 turbo with 162K.

Car smokes and misses at startup. The car was always warmed up when testing and checking prior to purchase... you know the story. I'm trying to solve the inherited issue with little luck. Otherwise aside from a couple small issues, it's a jewel.

Sometimes it smooths out and runs like silk with no smoke, other times symptoms persist. As it warms up and smokes it makes an occasional sound like a small dog sneezing as it misses, sorry thats the only sound I can relate it to.

The problem seems to be in cyl 6 as loosening inj line affects all but six. 1 and 6 injectors were swapped, symptom remained with 6.

Mechanic has verified IP delivery pressure is fine. He suspects a sticky lifter/follower which would explain the occasional smoothing out, or a bent rod which would not.

Has anyone experienced these symptoms and resolved them?

Want to avoid costly exploratory if possible. Your input will be extremely appreciated!