When you're ready to produce massive amounts of power and want the most airflow for your Cummins, you might want to condsider twin turbos over a large single. You get the best of both worlds with this setup. Quick spool up from the smaller Aurora 3000 and massive amounts of air from the Aurora 5000.  Lower EGT's and support for your electronic upgrades is what this kit provides along with the high quality you expect from ATS.

Here's what ATS has to say about their Compound Turbos:

The ATS Aurora Twin Turbo Kit is designed with performance in mind.  When looking for extreme performance with unsurpassed reliability, now you have a choice. ATS offers this Twin Turbo Upgrade Kit for the Cummins 5.9L Diesel for special applications such as heavy towing or extreme performance race applications.

This kit combines our Aurora 3000 turbo and our Aurora 5000 turbo which are designed specifically to be in a twin/compound configuration. Each turbo compliments the perfomance of the other,with the small turbo allowing quick spool up, and the large turbo delivering massive power and low EGTs.  The large turbo features a CNC machined forged aluminum billet compressor wheel, which sustains a very high pressure ratio without high mileage fatigue.  The small turbo features an extended tip compressor wheel to generate high boost without high mileage fatigue.  This system includes an ATS Multi-Piece Exhaust Manifold, which has pulse exhaust flow design, helping to spool up the turbocharger sooner with less exhaust backpressure and increased fuel efficiency.  This pulse manifold design eliminates the problems with shrinking and breaking, as well as cracking and gasket issues. 

NOTE: Head Studs are recommended whenever generating over 48 pounds of boost.
On Automatic transmission applications, the factory heat exchanger is removed.