Update -- I got the car back yesterday from the garage and it's running great. They replaced the injectors, then found the engine though running well lacked power. Some poking around uncovered air leaks in two of the three little air lines, one of which apparently leads directly to the turbo, meaning the turbo was not getting enough air to work properly. The mechanic said it looked to him like the holes had been there for a long time. Now everything seems in order, running smoothly and with a healthier sound I had forgotten hearing, little if any smoke at idle and little to none when driving. This last is huge because it's been smoking for two or three years, maybe longer.
As always, thank you one and all for your input, it helped get through the rough patches.