Look at these websites;
www.bavauto.com
www.turnermotorsports.com
You can spend about $1,900 and get a Remus exhaust, Jim Conforti ECU flash and an AFE cold air intake. It won't turn your 3.0 into a 4.4, but I would imagine you would be able to tell a seat of the pants difference with those mods. The ECU flash not only adds horsepower, but also allows a higher RPM limiter, which will means when you are accelerating hard you are starting each gear (after first) at higher RPM's and closer to the sweet spot for torque and HP.
If you want to spend twice as much and get the same check out
www.dinancars.com
It will be difficult and expensive to get an extra 50 hp out of the 3.0. Some of the people who own 3.0's and have done some or all of these mods may know better.