Hio. That all sounds good to me.

If it accelerates properly, I would say the timing is probably all right. I would still check it with a light.

My guess would be that one of the oil feed-tubes is leaking on the turbo - if he mixed any lines between the two turbos, they absolutely will definitely leak. I did this between two lines that even lined up right on my car and it caused me to dump 2 quarts of oil in 2 minute of running.

The turbos see very hot exhaust and have lots of surface area to absorb the heat. They are also cast iron, and distribute that heat quickly throughout the entire thing.

If the turbo is glowing, suspect improper valve(timing belt on wrong) or spark(CPS/ECU issue) timing.

The 90 is the first year with OBD1 - On-Board-Diagnostics. It's that little black block on the driver's strut mount. There are instructions on how to pull its codes in the FAQ. That could be useful.

First, some easy things to check - do you have full fluids? If you're missing oil or missing coolant, odds are that's what's making the smoke. Smoke doesn't come from nowhere.

If you think it's caked on gunk... clean it off! You can go after it with Simple Green and rinse that off with a squirt bottle. Only do this on a stone cold turbo NEVER A HOT ONE.

Good Luck and post back. Be logical and you'll figure it out. Some fluid has to be creating the smoke - either crusted on or leaking. Clean the turbo. Check your fluids.
Cheers!