As taz correctly said the earlier 208 gtb and gts were naturally aspirated engines from the 208 gt4. They are generally beautiful but very slow cars, with just 150 hp.
In 1982 Ferrari launched the turbo version, able to reach 220hp. You can easily recognize it from a 308 by the black details on the front and the additional NACA ducts on the car's side.
In 1986 Ferrari launched the last generation of these cars, following the 328's style. Those cars are called just "GTB Turbo" or "GTS Turbo", without 208, and thanks to the intercooler are able to reach 255hp and performance very close to the 328.
I know several people owning a 208 turbo and what I know from them is that they are not unreliable cars as it is often said but they need to be properly maintained, or the turbo could easily over heat and give issues. And, considering they have been quite cheap for many years, it is easy to find cars that had mechanical issues.
They are beautiful and rare cars (only few hundreds made), prices appear to be on a upward trend and the new F1 with turbo engines will for sure make them more interesting for any F collector.
"Engines are like women: you have to know how to touch them in the most sensitive parts."