93 octane fuel likely has something to do with it. After the install of the AMS downpipes and a Eurocharged custom dyno tune peak horsepower rises to 550 at the wheels. On the surface one might say 16 horsepower is not a large gain but one needs to look at the graph to see massive gains under the curve. With the new BMW turbo motors and how torque drops off toward redline as the turbos run out of steam major torque gains are going to come earlier in the powerband as boost is increased.
Once redline is approaching the gains level off but 48 peak pound-feet of torque gains are quite solid for a tune and downpipes on pump gas. This is something one will feel with the butt dyno the instant they put their foot down.
Graph and downpipe install pictures below.