DI means direct
ignition. That is a Saab proprietary innovative ignition system with one coil for each cylinder packed into a cassette above the spark plugs, which uses ion flow measurement in the plasma surrounding the spark plug to detect knock. This allowes to monitor the combustion in each cylinder separately, and thus adjust timing for each cylinder individually. Each charge can thus be ignited with optimum timing, riding the very sharp edge
just before knock would occur.
DI was introduced on the B202XL engine in the Saab 9000 turbo in model year 1989, and the two different versions (red and black, interchangeable only in emergencies) have been fitted to most Saab H engines since. The system is generally considered reliable, with the assumption that ist works flawlessly until it doesn't. Lifespan of genuine (SEM and NGK) DI casettes vary between 250.000 and 350.000km. Cheaper knock-offs have been known to fail earlier. Cassettes cost a few hundred euros, but can be changed within a few seconds, which is why experienced Saab drivers have a used, but known to be still working spare cassette in the trunk once the cassette on the engine reaches a critical age. Addition of spare cassette to trunk extends life of engine-mounted cassette indefinitely.
What most people mean when using the acronym DI (incorrectly!) is direct
injection, where,in contrast to port fuel injection, fuel is delivered directly into the cylinder. Direct injection allows both higher compression ratios and less enrichment under full load, both of whih increase efficiency significantly. Common issues that
may arise are LSPI, or, when the manufacturer avoids LSPI-conditions, fuel dilution; plugged dinjectors (which may lead to other symptoms ranging from bad throttle response and reduced power to holes in piston) and coked-up intake valves (which are no longer cleaned by fuel sprayed onto them, like with a port fuel-injected system.)
Direct injection may or may not be reliable and durable. I'd trust Toyotas and Subarus with their D4S-system (which combines both systems), I'd not necessarily trust other manufacturers and I do NOT trust VW and Audi especially.
Turbocharging is rather old stuff. The turbocharger was invented somewhat around 1905, if I recall correctly. It has been used on airplanes sine WWII, and on diesel engines since practically forever. Pioneers regarding it's use in passenger cars were Chevrolet (corvair), BMW and Saab, the latter being the first to use turbochaging not to increase peak power, but mid-range torque, thus inventing the concept that would late become known as downsizing. That was in the mid-70s. Since the introduction of the electronic boost control in 1982, turbocharged petrol enengines have become as reliable and durable as the best naturally aspirated engines when properly operated and maintained. Turbocharger failures and engine failures on turbocharged engines can usually be attributed to user error, ignorance, neglect, and/or stupidity.
Turbocharging can be combined with
any way of fuel delivery, ranging from carburettors and port-fuel-injection to direct injection.
So... to make a long story short, it is much more important
who builds an engines than wich technology/alpahbet soup the engine uses. If you are incompetent or cheapskate enough, you can [censored] up even the most mundane construction, while others can make complicated and advances stuff that is reliable and lasts...