Very much so.
Not just from one company/tuner either as there are plenty of companies who can do it as well as custom mappers. For example Revo, APR, Superchips, GIAC, MTR & more.
Also a stock car with no modifications can be greatly improved on with a new map. For example: "Revo Stage 1" software will take the stock power from 261Bhp to between 296Bhp & 311Bhp (depending on conditions, fuel etc). Stage 1 is £499 most places so a bargain really (imo).
Link: http://www.revotechnik.com/product-details/software/audi/s3/123/stage-1?ref=tsr-performance