it's not hard or rare to create maps for a turbocharged car. it has been done for every recent turbocharged car in history and its a well known fact among turbo enthusiasts.
personally i'd go with Shiv, just because his product is well documented on these forums, he communicates with the customers, he knows what he's doing, and Hartge's upgrade is probably marked up 1,000-2,000 beans compared to the Vishnu.
in a few years, after the new M3 is released, the 335i will be bumped up in the power department, probably using very similar techniques to what Shiv is using now.
oh the joys of turbocharged engines
